The Fascinating Reason Why The Garmin FR945 & Fenix 6 No Longer Shows Pool Temperature

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Back in August Garmin released a minor firmware update for the Forerunner 945 multisport GPS watch. On paper, firmware update 7.80 was about as boring as they get. The release notes only contained a handful of items, none of which appeared to be even glance-worthy. Here’s the official list:

“Forerunner 945 – System Software version 7.80 Change Log

  • Improve GPS ephemeris downloads
  • Fix a barometer issue that could lead to inaccurate elevation
  • Other minor improvements and bug fixes

Updates can be installed through Garmin Express or the Garmin Connect Mobile app.
This update is live as of 11:15AM CST 8/19/2021”

However, behind that curtain of mundane was actually a significant technical and customer support change that wasn’t oddly listed (in my mind, it should have been): Disabling the watch from gathering temperature data during a pool swim. Now – I didn’t say that it was a significant change to consumers. In most cases, you’d probably never have noticed unless I mentioned it. But as of that firmware version, the FR945 will no longer gather temperature data during a pool swim. It’ll however continue to do so in an openwater swim.

Turns out though, despite not being listed, someone did notice this change. And as usual, all broken roads lead to the Garmin Forums, where they posted their lack of fishbowl weather recording capabilities near immediately. And a short bit later, one of the Garmin customer support folks posted the reason why this was removed:

“The ability to measure water temperature readings during a pool swim activity was removed in version 7.80. After through testing and investigation, we have discovered that having the barometer-thermometer (a combined electronic part) powered on during exposure to chlorine dramatically accelerates the failure of the part. Therefore to give customers the best experience and product longevity we decided it was very important to make the change to turn off this part during pool swimming. “ –Garmin-Brooks

I found this randomly super fascinating (as did the DCR Reader who flagged it to me, thanks Tom). Not because I generally care about recording the pool temperature, but just about the logistics of figuring this out from a support standpoint. Garmin has recorded pool swim temp data on units with a barometric altimeter for years.  Here’s what it typically looks like for pool swims, summarized down at the bottom (this on a FR945 pool swim a while back):

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I tried to figure out exactly how far back Garmin supported pool swim temperature, and used the filtering options in my Garmin Connect account to see when it started. It wasn’t available on the Fenix 2 or FR910XT (despite having barometric altimeters, which in turn have temperature sensors). Nor the later 920XT or Fenix 3/3HR. Ultimately, the first swim files I can find in my history that have pool water temp is from the original Fenix 5, back in February 2017.  Meanwhile, the first Forerunner I see it in my files is the FR645 Music in March 2018.

But that trip down memory lane is beside the point. The point is this little line:

“After through testing and investigation, we have discovered that having the barometer-thermometer (a combined electronic part) powered on during exposure to chlorine dramatically accelerates the failure of the part.”

They go on to note in another short comment that:

“Open water swimming is unaffected this is only tied to pool swimming.”

Meaning, as specified in the original comment, this is due to chlorine and not saltwater. Meaning, you’ll still get openwater swim temperatures just fine, and indeed, my openwater swims show that’s true.

Of course, anyone who has been around the endurance watch scene long enough knows that the barometric altimeter port/inlet can often be the cause of altimeter-related issues (from many brands). Companies take great pains to try and ensure that the port on the watch leading to the sensor itself can easily be cleared of debris (such as dried sweat/salt, mud, etc…). Else, you get inaccurate altimeter data.

But there’s also been numerous cases on certain watches where there seemed to be a tie-in with people who swam a lot, and people who had more frequent barometric altimeter failures. With some people going through 2…3…4 watches via the support/return process (sometimes Garmin, but not always). But there’s never been a clear tie-in that I’ve heard to the chlorine in the water, and specifically having that part powered-on with chlorine causing issues.

I reached out to Garmin, curious if they’d expand any more on this. While they declined to, they did agree with a part of the e-mail where I said to them that this seems to be one of those things that “you only learn at scale”.

Meaning that this isn’t something any company would easily figure out unless they had vast scale or data points, or past experience with a very specific edge case (e.g. chlorine on a given component). Undoubtedly someone will say “they should have tested it”, the reality is – there’s simply no company in the GPS watch industry with deeper experience in watch components and altimeters. While Apple sells more units these days, they’ve only had a barometric altimeter on the Apple Watch for a couple of years in three models. Garmin, Suunto, Polar, and others have had it for more than a decade on dozens upon dozens of models. For example, here’s a swim in 2012 on a Suunto Ambit 2, that’s recording the temperate during a pool swim:

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Had this been a problem historically, they’d have caught it years ago. Thus, clearly something changed with the exact component being used in the FR945 (or, a batch of watches in that timeframe). Components change all the time in watches as component suppliers update said components with newer versions. If this was a problem across the industry, someone would have realized it by now and shut off pool swimming temp.

The whole at-scale thing reminds me a bit of one of my favorite endurance sports tech quotes, from James Meyer, one of the co-founders of Quarq power meters (now part of SRAM). He said, paraphrased, ‘When you build your first 100 power meters, you think you know a lot. Then when you build your first 1,000 power meters, you realize how much you didn’t know back at 100. Then when you build your first 10,000 power meters, you realize how you didn’t know back at 1,000, and so on’.

Undoubtedly, based on Garmin’s “extensive testing” comment, there are probably massive e-mail threads and documents within the company now on how to test components on watches with probably not just different chlorine levels (and being powered on), but also other water salinity levels. And since this thing is something that isn’t just ‘test once and be done’, but rather longer-term life stuff – I’m sure there’s even more tests on how they onboard new components from suppliers in this area.

And also undoubtedly, I’m going to take a guess that every other company in this space is now forwarding this post around, looking up in their customer service databases around barometric port failures, to see if there are patterns around pool swimmers and higher rates of failures. I wouldn’t be surprised to see the pool temp data field disappear not just from other Garmin wearables, but from others’ watches in the market. Many companies in this space use the same component/suppliers. On the Garmin side, I noticed my FR745 no longer records pool temp data, which is a watch that likely shares most of the exact same components as the FR945.

And, in the Garmin Forums, Garmin worded it slightly differently on a recent Fenix 6 firmware beta release. Albeit, folks with the most current production version are still seeing pool temps. So either this change is still incoming, or changed direction.

“Our Fenix 6 series engineers have chosen to disable the temperature sensor for the Indoor Swim APP only. The intention is to improve reliability of your temperature sensor along with other sensors.” -Garmin-Chris

Will this meaningfully impact many people? Nah, not really. Some have argued that having a separate activity profile for ocean-fed pools (which aren’t chlorine) would still be useful. And true enough, it would. Though I could see it’s probably a bit confusing from a user interface standpoint.

In any event – I found this interesting, and I figured I’d share it.

With that – thanks for reading!

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122 Comments

  1. Thomas

    Very interesting.
    My Fenix 5s still shows pool temperature. I actually would have been one of the persons who noticed it, because from time to time (when I get out of the water and are really freezing), I check the temperature of the pool on the recording afterwords. Mostly because I want to know if I have a good enough excuse to take the wetsuit next time or not 😉

  2. Benedikt

    Im on my third 945. The first one failed after a freestyle swim workshop last year, the second one this year. Both times the barometer started making a pancake flat Rhine area look like the Alps.
    Also, i never got why Garmin enabled recording of the internal Temperatur. It’s always wrong and always starts unnecessary discussions in their „backyard“, the forums. And not only once per device.

    • Kevin

      On my 935 I’ve found that the only time the internal temperature is representative is during swims, where the influence of your body heat is negligible. At the moment, it still records pool temperatures (different hardware?) but I wouldn’t be fussed about losing it. I’m glad that this issue does not impact open water swims as it’s reassuring to see it was actually damn freezing and I’m not just going soft.

    • Benedikt

      I think the 935 is a different hardware. In open water swims im with you, its interesting to see the water temp there.

    • Duncan Tindall

      The FR935 failures of the barometer are legendary. So I wish they would disable it on that – Garmin has replaced thousands of FR935s (based on posts on here and slowtwitch and their own forums).

      However, I am slightly reassured now that they have this finally sorted and they are no longer in denial.

      Note that the lack of pool termperature was never an issue anyone cared about. It was the fact it blew out the altimeter that meant all the uploads from any activity suggested you did it around a canal path at the top of everest, and you couldn’t make Garmin Connect DEFAULT to use the elevation correction for a watch with built in barometer/GPS.

    • Kevin Dwyer

      If they were in denial it wouldn’t be an issue as it is a fresh water river.

      Sorry, I’ll get my coat…

  3. Dave Lusty

    But have they identified a better component to use going forwards? It’s one thing to identify a problem but quite another to fix it.
    A lack of pool temperature doesn’t matter to you or me (although as a data nerd I like all the stats!), but I bet pool temperature is a data point used in analysis for a lot of swimmers, and could potentially also be used to tweak training plans at the poolside when its effect is known. It would be a shame to see Fenix.Next arrive without this being sorted. Perhaps Fenix.next.next would be more fair if this was only discovered recently, hopefully they’ve already ramped production of the next version!

    • Benedikt

      If you use pool temp to tweak a training, why not put it into the notes of the activity? All pools i know puplish there water temp, several times a day.

    • Dave Lusty

      If I wanted to take notes I wouldn’t have spent a thousand bucks on a sports watch. I can also easily draw my track on a paper map, but that’s not what we’re going for here!

    • usr

      Impossible to disagree with that. I wonder if Garmin might be looking into the question of wether it’s the kind of component failure that creeps in over time or wether it’s more a “per session” pattern where it would not make much of a difference if it’s five minutes or five hours. If it turned out to be the latter, they might re-enable pool temperature by firing up the sensor once per activity, after a sufficiently long exposure to have the device reach pool temperature.

  4. Actually I have to say this is pretty disappointing because I use the temperature reading all the time for my pool swims to understand performance versus temperature. I stopped swimming at a pool because the temperature was consistently creeping up. I could feel it but was the empirical data that it was actually increasing and I wasn’t losing my mind 😉.

    • Don’t most pools though post the temperature? Sure, not ocean-fed ones and such.

      But almost every pool I’ve been to has it posted somewhere usually – even if out of the way (namely because staff/lifeguards usually record it as part of pool records).

    • Dave Lusty

      They do, but how do you automatically record that with your other data? The whole point of a sports watch is to automatically record data for later analysis. I’m OK with this being an issue they found, we all make mistakes and things don’t always work as planned. It does need fixing going forwards though.

    • I don’t disagree there, though, for Chris’s purposes I assumed he just wanted to know the temperature somewhere.

      But yes, if someone is trying to throw the gauntlet at their local YMCA about pool temps, then having automatically gathered data for months is useful. I mean, up until the moment the water aerobics mafia grandmas meet you out back for trying to lower the water temp. At which point, data ain’t gonna help ya there.

    • Ray

      Actually the pool temp for us wasn’t posted or shared. The pool had a new supervisor and I had to complain when the pool was unfortunately warm at 87 and he thought the compromise was 84 which still made the swim no fun. Found a new pool that is steady at 78..it is heavenly 🏊

    • Nic B

      Went through about 3x 935s due to barometric pressure functions failing when I was pool swimming 3-4 times a week training for Ironman. I didn’t realise it was because of the temperature reading being used

    • DanW

      I have gone through 3-4 935’s with the barometric pressure function failing as well. I swim a good bit. Will Garmin push through a similar “update” to the 935 or can I disable it?

    • Mark R.

      Hilarious.

      I regularly swim at 3 pools and a lake here in the UK, the only one that posts the temperature….?
      You guessed it, the lake!! …plus they always exaggerate the real lake temp by +1C, and my Garmin 935 always calls them on it. 🙂

    • Nemo

      “up until the moment the water aerobics mafia grandmas meet you out back for trying to lower the water temp”
      This cracked me up- such a universal truth!

  5. william McAnirlin

    interesting. I contacted Garmin yesterday as the Baro/Altimiter just started to fail (i do not usually do 60k elevation on my runs) and they have agreed to replace even though it is after the warranty. I suspect this would be the issue.

  6. JeyJey

    Hi Ray, glad you posted this topic in your place. I am one of the many people that they realize about this major change without being advertised. In fact you posted my forum topic that I wrote on the F6 Garmin forum, answer by Garmin Chris and then locked. I don’t usually participate on forums or comments but I read a lot about theses devices and for me the lack of reading water temperature is a bigger concern specially here in Spain that we have many open air swimming pools to practice our sport. It give me a very valuable data that I found so useful and accurate. I wonder if the Garmin Swim 2 watch has also disabled this feature (if it has, I don’t know) and if the tests that you comment above were taken from that device because it is used mainly by this kind of athletes or maybe is another Garmin “brilliant idea” from someone from their management. Another interesting topic that I realize is a Garmin Iq app that disappear from the market, it was called “fever monitor” more strange was that it was initially awarded on the Garmin Iq developers and then disappear both from the app store and from the Garmin blog where it was mentioned. For your information and if you want to continue investigating 🙂 rare things from Garmin. Thanks for your reviews keep them going!

    • Yeah, I definitely understand the ocean-fed pool scenario (also popular in Australia for example).

      I could potentially see a setting in the pool settings menu, the same way you setup the pool size, that’s mostly hidden – but is there for folks that want it, to enable temp readings in the pool. And then perhaps each time you go to swim it’ll flag it (just like Garmin does for calibrating your power meter) to confirm it’s not a chlorine pool.

      Not sure on the Fever CIQ app. I know Garmin has flagged apps in the past that make medical-ish claims and/or safety related claims (e.g. a diving depth app). That said, given this wasn’t just a random app in the app store, but one Garmin actually gave an award to, it would have been heavily discussed by that team prior to the awarding. Instead, it wouldn’t surprise me if the developer themselves pulled it for some reason. I noticed that developer account shows as present, but without any apps published at all right now.

    • Tomasz Grabowicz

      Maybe swimming in the pool is “not cool” for Garmin. Why even bother with some geeky stuff like “temperature” or length or stroke. For me, great news. Open water swimmers unite. GPS bizarre errors for us, no temperature 🌡️ for them.
      All I want is New Badge.

  7. harmen

    I’m on the very latest firmware (16.90) for the fenix 6 and it happily displays temperature during pool swimming and shows it in the Connect records. Is this part of a release that has not yet been rolled out globally or has it already been reverted?

  8. Howard Waller

    Cool. I bought an old Garmin Swim for pool swimming specifically because of this problem. Although it means swapping watches before I swim, I didn’t want my fancy new multisport watch to malfunction because of the swim/barometer problem (I had a 910XT that did exactly this, replaced under warranty).

    • The good ol’ Garmin Swim (OG/V1) – arguably one of the greatest watches Garmin has ever made that almost nobody ever knew about. Lived in my gym bag forever, no battery charging required.

      For folks that want some memory lane: link to dcrainmaker.com

    • Steven Knapp

      I wish I liked to swim as much as I liked that watch.

    • Dave

      Agree. I loved mine, but killed it when I jumped into the Parnell Baths (salt water) pool in Auckland and somehow popped the back off (I still don’t know how I managed this). It filled up, died, and went in the trash.

  9. So you wouldn’t say that it affected previous models? Curiously, perhaps coincidentally, my Fenix 3 ABC meter failed this summer in the same vacation where I swam in a pool for the first time in years!

    Also, this leaves me wondering: can I safely swim with my Fenix 6 in a pool? It’s disabled in the activity, but what if I jump in a pool without starting an activity? Won’t the sensor be on for its regular readings? Will that impact the device’s lifetime?

    This seems like a serious issue and definitely not one that should have been hidden from the changelog.

    • Hard to say on previous models. My guess would be that if we start seeing old firmware updates with it being disabled, that’d answer that.

      But yes, I’d agree that standby use such as jumping in a pool would seem to be the same. However, it’s also possible that in standby usage Garmin might have significantly lower temp/altimeter polling (meaning, perhaps for workouts it’s at 1s intervals, but for standby it’s at 1min or something else). Not sure offhand.

    • Benedikt

      I think, there is something electrochemical happening to the sensor. If you jump in a pool while outside of an activity, the sampling rate of the barometer is much lower. Thus, the reaction is running a lot less often. I don’t imagine it to be a digital failure (it’s good and zack, now its bad) but to be a creeping corrosion sort of thing.

    • Such a change in range of operation would surely warrant clear communication from garmin.

      I guess it’s clear from my previous message that I hardly swim. But that just means all the more chance to potentially forget that the device that I payed plenty for, with under-water capabilities up to 100m, could break from my one-off plunge in the pool unless I think of actually starting a pool swimming session.

      And I probably won’t remember, given that my swimming doesn’t resemble anything like ‘sports’, and mostly is focused on ‘not drowning’. 😏

    • I agree that your hypothesis of corrosion through electrochemical process is quite likely. Hopefully the sampling rate indeed makes a large enough difference here.

  10. Tom

    That was fast!
    I knew the geek in you would be interested 🙂 … thanks for the post and for reaching out to garmin … unfortunately not much further details on clorid ion flow and conductors and what not …

    Transparency by Garmin could have been better, but overall good catch and fixing decision by Garmin.

    Keep up the good work Ray!

  11. Peter Flur

    There have been barometric issues since the 910 if not before. I’ve had every version since replaced several times when it failed. 910. 920. Fenix 5. Fenix 6. Fenix 6plus. Garmin always replaced although they often made you jump through hoops like resetting back to factory settings.

    The consistent difference among our group was that people who swam in the pool had problems. Those that didn’t didn’t.

    • “The consistent difference among our group was that people who swam in the pool had problems. Those that didn’t didn’t.”

      Definitely, as noted in the post. However, I wouldn’t necessarily assume that’s tied to the exact same chlorine-specific altimeter-on issue. After all, the 910XT and 920XT didn’t record water temp in pool swims.

      It could very well be tied to other water-related things with the port design or such. Or maybe it’s the same. But as noted, in general, if I step back and look at people across all manufs (mainly Garmin/Polar/Suunto), the clear pattern for altimeter failures is people who swam significantly more – both inside and outside. But of course, the altimeter port is the only hole in the watch where water can get in.

  12. Nemo

    I have to say I’m actually relieved to hear this! The barometer on my Fenix 5S failed a few years ago despite several rounds of troubleshooting with Garmin. Ultimately they suggested “rinsing” the watch after swimming in a pool (and the new Fenix 6 manual now contains that similar instruction in Device Care). I now have a Fenix 6 and have been rinsing after swims (though I admit not every time) but have been basically just waiting to see how long it takes before the barometer breaks again. I’ll take a working barometer over knowing what the pool temp was on a swim any day!

  13. tim

    Interesting post indeed. I was just reviewing past OWS swims for temperature data to estimate our local lake temperature for a friend and for fun looked at a recent pool swim with my 945LTE running the latest beta.

    A few comments:
    Even though the temperature field shows a plot during my OWS (as if live logged) the data seems questionably accurate. Last week’s swim implied 70F water, a possibility, but I went back to a swim on June 11 and it showed average water temp of nearly 90F. Maybe I’m wrong and this was reality, but in our area most people don’t even get in a lake until around June 1 due to temperatures being low 60s.

    With the pool swim this week, on 945LTE beta 4.07, temperature is still recorded. Should I be worried about a baro failure?! I guess I assume they will be removing it eventually?

  14. Alan C.

    I’m confused about the statement in the last full paragraph about having separate profiles for Open Water vs. Pool Swims. My Fenix 5 has those two separate profiles, so presumably the water temp will work for Open Water?

    • “Some have argued that having a separate activity profile for ocean-fed pools (which aren’t chlorine) would still be useful.”

      In this case, I’m referring to the request some have made on having two *pool* profiles. One for ocean-fed pools (or any non-chlorine pool really), and one for regular pools. As you noted, there’s already an OWS profile, but that uses GPS and won’t work in a pool setting.

  15. Povilas

    Interesting stuff. I had my Fenix 5s replaced twice since 2017 due to failed altimeter/thermometer sensor. Last time Garmin replaced it even the warranty has been already expired, never got any explanation on what might be the problem though. First time I thought it was just a back luck, but the second failure more or less coincided with me getting back to pool swimming.
    It does not seem that this update made it to 5s yet and the watch is still recording temperature in the pool. I wonder if Garmin found some kind of solution for 5s or just haven’t prioritized updating it. My current watch shows no signs of failure yet, even though I have been going to the pool regularly for the last 6 months. I’d very much like it to stay this way.

  16. Pascalwb

    Kind of sad, I just got venu 2 and yea there is no temp. Had V3 M before which showed it, but died. I feel like they removed it from website too, because I don’t see it on my swims, but it was there before.

  17. Lead

    Another interesting angle to this: many pools (in the US at least) doubled their free chlorine concentrations during the COVID epidemic. It would be interesting to know if this higher level of chlorine exacerbated whatever reaction is occurring with this part.

  18. Andrew B Goetz

    Wow, I just asked about this problem back in July. Garmin just told me mine had failed and then they charged me $200 or so dollars to get a replacement. I asked could it be the chlorine, because the pool I usually swim in is terrible.

    See attached. I swam that day at Deep Eddy Pool in Austin, TX the pool is a constant 70 degrees not 109.4. I like knowing the temp, because all the YMCAs I swim at here in Dallas, TX never know the temperature of the outdoor pools or indoor pools when you call ahead of time. Therefore I can tell a friend if it is to hot to swim or vice versus.

  19. Manev

    Fenix 3 measure temperature in the pool.
    You can see on the picture. Peaks of temperature are showers before and after the swim. Between them is pool swim. I checked in Garmin connect – there is no info for temperature for this pool swim activity. May be it is not recorded in fit file but it is measured.

    • Interesting. Yeah, it’s not in any of the Fenix 3/3HR swim files I have on Garmin Connect.

      The widget you have there is the general 24×7 one. I don’t know offhand the exact differences in update rates between the two modes.

    • Anders Majland

      My Fenix 3HR also showes the graph above with pool swimming – but never bothered to look at the temperature afterwards in garmin connect.

      Since i got the Swim2 a few years back i’ve not used the Fenix 3 HR much. But do take it with me ocaionally for the temperature (and a back backup track) openwater and might also have a few pool swims with it.

      I’ve just looked at carming connect and even my old 2019 pool swim with the fenix 3 hr is now without temperature -but the openwater is

  20. Leo

    I really don’t understand why such a lengthy article is written while you can be so clear about the temperature measuring capabilities of any garmin watch: it doesn’t work. It always measures somewhere between bodytemperature and outside temperature, so always wrong.

    (yes, I know, the garminfanboys are there to point out that you can take your watch off and leave it in the area you want to measure for about an hour and get a good reading. Yeh, that is a realistic use case)

    • Generally speaking, cooler moving water temp isn’t going to be meaningfully impacted by your body temp. It’s constantly being refreshed as you swim (given all the movement), far faster than you can possibly heat it. Thus, as many have shown – you get a reasonable estimate of the water temp.

    • Leo

      The only time I can check is in an indoor swimming pool where they advertise the water temperature and my watch is always higher than advertised.

      Are you sure people don’t just guestimate and tell the water feels the same as their watch shows?

    • This isn’t really some newfangled thing. As noted, this has been on watches for nearly a decade now – and for the most part, it seems to work as expected in the water.

      As noted, outside the water in the air, then no, it’s going to be higher (how much varies exactly on the conditions) and whether you have other layers on.

  21. I am SO relieved to see that there is finally an acknowledgment of and hopefully solution to this problem. At one point I noticed that the pool temperature info disappeared from my stats and realized that’s the same time my elevation info went bad. I’ve been living with watches that tell me I had 1,800 feet of elevation on my flat rail trail runs ever since. Eventually I began to suspect that it was from swimming in a pool several times a week, but I kept reading that supposedly it wasn’t that common of an issue which added to my frustration. It happened to me 3/3 times, how could it NOT be a real issue?? It happened on my 910. Eventually I moved on to the 935, had it a few months, the elevation went bad. Sent it back, a few months later it happened again. After having it happen on three watches I gave up because I didn’t want to keep sending them back. Although I like the familiarity of my Garmins, I was convinced I’d just be asking for it if I bought another one in the future. I’ve been pretty annoyed living with useless elevation info for years. If I can be reassured this won’t just happen on the next watch I buy, maybe I won’t switch brands after all.

  22. Nate

    are we getting any new garmin watch releases in 2021?? trying to hold out.

  23. Anthony LoSasso

    Really interesting! I’ve owned a succession of FRs (920XT, 935, 945) and all have experience barometric failures (as judged by ridiculous elevations in pancake-flat Chicago). I’m on my second 945 right now after such a failure after only 6 months of use. Here I was thinking *I* was doing something wrong & letting junk get into the barometer hole!

    As an aside, this kind of reporting is why DCRainmaker is the best.

  24. Rafael Martinez

    Didn’t know temp had been recorded…but that is not important to me, however distance is.
    Why with the 945 I always record more distance than actual (the apple watch is spot on, everytime)?
    e.g. yesterday I swam 2 sets of 1000m, each time the Garmin said 1075. Annoying!

  25. Paul Furniss

    I was the person that noticed the lack of temperature, Garmin had me send in my whole Garmin folder from my watch, I don’t think support knew that the engineers turned off the temp feature. It still shows up on Garmin Connect.

  26. Volker

    Maybe a stupid idea: what is with mounting a Garmin tempe sensor on the strap of the watch? Because of the short distance, it showing the temperature even under water. Can’t attach a pic here, but have put my F6xPS with a tempe sensor on the strap in a bathtub full of water and the values ​​are displayed.

    • Dirk

      I was thinking the same, great you tested this out (and that it’s working)! Not sure if the Tempe is fully waterproof though (I’m guess that’s not the case). Maybe it’s only a matter of time until Garmin is releasing a waterproof Tempe (with memory option, like a Garmin Swim HRM)?

    • Volker

      You are right, it has only 1 atm, so not suitable for swimming.

  27. Alex

    Hi Ray, maybe you could write a similar post on how the Index S2 scale BF% is broken since the release and essentially a random number generator, moreover, the new Garmin fitness age metric is influenced by BF% and the results are completely off, to say the least.
    Please check Index S2 forum thread.
    I have single digit BF% but S2 keep showing 18-19%BF

    • I’ve been talking about how electrical impedance scales for body fat are pretty much not dependable for a decade: link to dcrainmaker.com

      I noted the same in my Index S2 review, even linking to that post. Nothing has meainginfully changed in that technology area in probably 20 years.

  28. Monica

    I’m on my 4th 935 due to this failure – the failures all happened during a race build where I averaged 25k yards/week, most of which was in the pool. My elevation still doesn’t really work but I got sick of sending watches back to Garmin especially when elevation data isn’t really critical to me these days

    During one of my million customer support calls (early 2019), the Garmin rep told me it was critical that I rinsed my watch in fresh water after every pool swim, so they’ve had an idea on cause for this for a really long time.

  29. Scott

    My 945 LTE is still recording temperature during pool swimming. I wonder if this newer model has different hardware? Hopefully that instead of Garmin just not having enough failure data yet.

  30. Joel

    Awesome… Now do it on the 935…

  31. RICHARD OWEN

    I have had 2 barometer failures on a 935 and 945 – both when I have been doing pool training (only 3-4 months of the year). Could be a complete coincidence of course. Pool temp is ‘interesting’ but I’d much rather have a functioning barometer for runs / rides etc.

  32. This was a fun read 🙂 I’d actually disable temperature data if not connected to the Tempe if I could. It is just something between body and outdoor temperature. So kind of makes the fit file bigger for no reason. Worse, if there will be a metric that will use this later on, its history data will be completely skewed. But afaik I can’t turn that off.

  33. Peter Z.

    Glad to hear they will support for open water swimming. I was just wondering yesterday if that was a feature. I thought maybe having on body could throw off temperature

    On a related note for barometer failure, my Vivoactive 3 altimeter is inconsistent now. It will show different altitude when I start and finish at same location. I did try cleaning out the sensor opening and soaking bit has not resolved

  34. Shirley LeMay

    My first Fenix 5s Plus’ Altimeter / Barometer / Temperature meter failed after 14 months of use. I swim 2-3x a week. I paid for a refurbished replacement (Garmin gave me a $50 discount as a bone) and that one lasted less than a year with the equivalent of 6 months of swimming (pandemic closed the pools).

    If I buy another Garmin, I’m keeping the Fenix just for swimming which is sad since these watches aren’t cheap!

  35. Hop Bailey

    Thanks very much for publishing this.

    I went through seven (seven!) 935 temperature sensor failures, all within the 3-month return period except for the last one and got a new watch from Garmin without charge (although they sometimes had me pay shipping). The seventh one lasted about six months so I carefully evaluated the 945 and bought one about a year ago. The temperature sensor recently failed.

    I swim everyday in a pool so the I’m a good example provoking the failure mode. I did check pool temperature everyday. I live in Arizona; all the pools are outdoors and it is very hot in the summer so getting the pool temperature is a useful thing. I checked the in-water watch temperature against standalone thermometers and it agreed quite well since in the water body temperature was overwhelmed by the surrounding thermal mass of the water.

    Since elevation changes in running, etc. are determined by the barometer-temperature and my sensor has clearly failed I assume my 945 failure has permanently nuked elevation measurements. That certainly sucks.

    I’m not buying the claim that Garmin did due diligence on this problem. My 935 temperature failures took place over a period of about two years and that was before the 945 was announced (giving them a chance to make a part replacement or discontinue pool temperature measurements). Others were reporting similar failures on the Forum so I was not an isolated case. Imagine Apple pushing out an iPhone with a defect like this. Oh, well, they did. I had an iPhone 6 that had a systematic problem with an internal connector. When I brought it in they replaced it for free with a new model that worked. Garmin just left me holding the bag. So I’m thinking a Coros Pace 2. Why pay $600 for a defective device?

    Love DC’s posts and YouTube reviews. They are the best.

  36. Karsten

    My Fenix 6 19.20 still recording (overheated) pool temperature two days ago…

  37. L

    My Descent Mk2i shows pool temperature, and it has a barometric altimeter. Seems weird that they’d remove it for some models and not others.

    • Dave

      Maybe a component replaced/modified? BTW, how are you liking the Mk2S? I’m very much on the fence between waiting for a 7 Solar and just getting the one I’ll also be able to record with / use on the rare occasions I’ll dive/spearfish.

  38. Steve

    Corrosion from chlorine would be a problem in pools and ocean for the sensor. To me or makes no sense whether it is recording data or not. Either way the sensor is exposed. Here is a website that talks about corrosion in temperature and pressure sensors.

    • Dave

      I suspect it’s more to do with how electrolysed chlorine degrades materials, rather than a simple matter of corrosion. I’m not a chemist, but I suspect that an acid is probably produced, creating some kind of small scale cavitation. I bet a close up of components would show a lot of micro-pitting.

    • Ted

      Corrosion from chlorine on the sensor would be PRESENT in pools or the ocean. Not necessarily a problem.

      The magnitude of the corrosion in a freshwater pool environment (hypochlorite ion) is why the barometer/thermocouple is deactivated (powered off) during pool swims. Hypochlorite is more corrosive to the metals used in the thermocouple than the predominant chloride ion found in seawater (or in seawater pools). By powering down the thermocouple (and with a side-effect of not having temperature data to record), the effect of hypochlorite-induced corrosion is reduced on the thermocouple metals.

      I can’t say what percentage of open-water swims are in salt water vs. fresh due to lack of data on my part. I would assume that most open water swims are in freshwater, which is ONE reason why Garmin left the thermocouple powered up for open water swims. The open water swims on a Garmin device are not delineated between a salt water swim and a fresh water swim.

      Another consideration is the actual materials (metals) used in the Garmin thermocouples. In industry, thermocouples can be made with different metals for different temperature ranges AND different working environments. Perhaps the metals in the TCs used in the Garmin units just have shown that they are not durable for long-term use in a hypochlorite (freshwater pool) environment, and the corrosion in that environment is shown by data to be accelerated when the TC is active.

    • harmen

      Is there a difference between chlorinated freshwater pools and saltwater (but not seawater) pools? I understand they have the same levels of chlorine, but that the saltwater pools don’t have all the bleach. Would it be safe to use a hypothetical saltwater pool profile in a saltwater pool that is not simply ocean water?

    • Dirk

      Not sure if the temperature sensor in the Garmin watches (or other wearables) is of the thermocouple-type. I would rather think its a resistance-type. But either way, it seems there is indeed a problem with the hypochlorite present in swimming pools.

    • Tom

      With regard to “the effect of hypochlorite-induced corrosion”: Would the barometer become less and less precise with time…or would it just switch from producing ok values to nonsense at one point in time immediately?

    • Lazaros Filippidis

      In my case the 935 gave out ever so wrong readings (not sure if it has the same hardware or similar with the 945). Initially the error was a few 10s of meters, then couple of 100s, then quite a bit more. Check the image, that was a run on track!

  39. Dan

    I had this exact issue with my Garmin 935. One day the alitmeter stopped working and I read it was related to using your watch in the pool. Great if this solves it as while Garmin customer service were great (replaced it even out of warranty – it’s a pain to go through the whole process of returns.

  40. Herbert Poul

    Good catch, I was really confused that the watch didn’t show temperature. Thought I might have misconfigured something.
    Sounds really interesting. Especially since i guess there is no mechanical way to keep the clorine water away – what’s the difference between having it powered on vs. off? And what happens when I don’t perfectly rinse my watch before heading out for a ride after a swim 🤔️🤨

  41. Ladislav Novak

    When I saw Garmin watch on the screen, I thought hurrah. My Garmin 935 a week ago stopped working and I’m looking for a replacement. I peel off the tablet, go make myself a cup of tea and then I start a read. But wait a minute the text is about the temperature in the pool? Somebody is kidding me? Anyway back on track and I am trying to find some replacement of my nonworking Garmin 935 – good work Ray!

  42. Dave

    This definitely explains why a lot of people I train with have had to have their Fenix 5 series watches warrantied. All of them had altimeter/barometer failures. Interesting.

  43. Morey000

    I’m the guy that started at least one of the pool swim temp threads over on the forums.

    Question- the Avg/min/max temp (the thing you have your big red arrow pointing towards in the figure above)- still shows up at the end of every pool swim. We aren’t getting a continuous temp display, but we’re getting something. Are they just taking one reading and shutting it off? like- what’s going on with the new algorithm?

    To answer your question above Ray- no, the pools in my area don’t post the temp. They also get super warm in the summer, exceeding 90F at times!

  44. Tomas

    Interesting reading! Is this potentially an issue for Garmin Fenix 5 plus? Or do those watches have different hardware than F6/FR945?

  45. David

    My takeaway from this post and the comments… I obviously don’t swim enough. My 920xt barometer only crapped out once the warranty had long since expired and my 935 is still going stong after 3+ years.

  46. ChrisTexan

    Very interesting! Wish I had time to dive into the internals of a few models, maybe at some point I will. But seeing this makes clear it’s some sort of galvanic/electrolytic reaction, which also means that for the affected models, there is some exposure of a metallic component of the sensors to the water. Most likely this begins a corrosion or deposition issue that then puts pressure on, blocks, or erodes into, the barometric sensor itself.
    Only the vendors, or those willing to do a very high risk of “destructive” teardown of the watches, will likely be able to see this directly.
    On my v800s, I currently have one disassembled, (my older with ailing (not failed, but not usefully functional) barometric sensor, for a battery swap pending. I actually attempted to disassemble the barometer “port”, which is a silicon cap with small pitot tube, adhered (unfortunately) to the top of the sensor itself. Because it seemed pretty firmly adhered (more firmly than I wanted to risk breaking by disassembling, I tried with significant careful prying, shimming, and pulling to remove the cap from the main board), I didn’t want to proceed further as if there is any adhesive involved and it’s touching the gel seal on the sensor, removal would certainly be destructive beyond the levels I attempted.
    All that to say, baro sensors come in a variety of styles. Some (many) are a metal “shell” with nothing but a tiny sensor hole, encapsulating the actual device (for ruggedness basically). Some are plastic shell encapsulation, some have built-in pitot tubes, etc.
    Some are fully open and “leave it to the designer” on what to do with them. I’m suspecting based on it’s design, the polar v800 at least has an “open” design, based on how the silicon seal/pitot is designed for it.
    All that background to suggest, the FR945 and similar, sound like they may be a metal-shell encapsulated part with an exposed thermometer/probe sensor inside (nearly all baro sensors have a gel-protected “membrane” over the actual baro pressure sensor itself, but it’s possible these do not and are directly exposed to the pressure-sensing surface, especially if within a hardened PCB metal shell)… either of those scenarios could lead to a galvanic reaction for sure when powered, versus a gel-sealed, plastic/silicon encapsulated environmental-isolation model which would almost certainly would not be bothered in the least by chlorine exposure.
    So it’s likely as you (Ray) said, I’m sure a lot of engineers at the watch firms are going to look at this to determine what they’ve used, and if necessary, is there a simple “swap in production” part available to ameliorate the issue moving forward (very likely, as someone who has researched these in the past, vendors make dozens of very similar “styles” for various purposes, literally a single pressure sensor may have a dozen or more variants of encapsulations, ranges, etc.
    Those using gel-sealed plastic SMB parts, are likely to have little to no concerns at all. Anyone else, definitely needs to consider the materials and reactions possible.
    … okay, curiousity got the best of me, so dug up the internals of the FR945. It DOES appear they are using a metal-shell sealed barometric sensor (rather large one at that given the application!), which would potentially not react well with chlorine when energized (the shell itself is almost certainly grounded to the negative circuit, thus any stray positive voltage from the sensing units themselves (possible thermocouple exposed inside the shell making contact with the water if I had to guess, or even poorly sealed surface traces eventually becoming exposed to contact) would start a reaction.

    Should be interesting to see how it all plays out!

  47. EH

    It would be interesting with comparison of the accuracy of the altitude between the different GPS watches

  48. ReHMn

    There should be a device software update archive to let the users decide, what SW version they will be using…

    Somebody should explain to Garmin, that Ozone replaced chlorine in pool disinfection a long time ago…
    My swimming shorts can prove it.

  49. Lazaros Filippidis

    Don’t tell me that the 935 failings in the barometer are caused by this hardware being enabled while swimming in the sea….

    • Nobody is saying that. The differences between sea water and pool water, and how they impact certain components, are outlined in both the post and in far more depth in some of the comments.

    • Lazaros Filippidis

      thanks, I realise that, it is just that I’m on my 3rd 935 with this exact problem (barometer showing wrong values).

  50. Eli

    Chlorinated water and salt water conduct electricity differently. So they just need to add skin conductivity sensors (gsr) to measure stress

  51. TravisM

    I guess that’s what happened to the temp sensor on my 935. At some point it started reporting -173* for the temperature all the time.

    • These sorts of bugs are weird to me – like, how does the code even allow that?

      For example, Garmin has many filters in place in numerous spots on both device and web/app that block clearly erroneous values. Stuff like 10,000w from a power meter, and hugely negative elevations (slightly negative is OK). But -173* (C or F) is well below the coldest temp ever recorded naturally: link to en.wikipedia.org.

      (There’s your daily Wikipedia distraction starting point…where you can find out about the coldest temperature every recorded involving something called a ‘Nuclear Spin’, which was my cue to close the tab before I’m here until next week clicking Wikipedia links).

  52. BuTTuS

    Off topic, but Ray, do you have any information about the Garmin outage regarding 7 days training load and VO2 max?

    • Which outage is that? I don’t see any outage here: link to connect.garmin.com

      And I’m seeing training load and VO2Max on my FR745 just fine from workouts this weekend.

    • BuTTuS

      The 7 days training load and VO2 max graph have not updated for a week on the web and in the app

    • Huh. Interesting. I see it on Load focus, exercise load on app, but yeah, the 7-day load doesn’t show last 7 days. I virtually never dig there, and just look at it on the watch, but yup, now I see it.

      That said, Vo2Max in-app does show updated for me on app graph (including yesterdays)

      I’ll flag it over and see what’s up.

    • David

      I noticed this too. And for me it happened to correspond exactly with when I got a new phone. I’d assumed it was something to do with my new phone. Also I have no body battery data on my phone (but it is in the watch).

    • Well, for whatever reason, the 7-day training load seems to be fixed this morning. Someone must have kicked the server Monday morning when coming into the office…

  53. Zoltán

    I am on just on the other side as regards the availability of the internal temp sensor. I would be extremely happy if it could be disabled in sensor menu of my Fenix 5 plus.

    I dont speak about a full shutdown, it may work if it is needed for altitude/elevation calculation, but I mean a knock-off of the internal temperature as a data source of Temperature data.

    I have 3 Tempe sensors and I hate those moments when the connection between my watch and active Tempe is broken for a while and the temperature of the internal temp sensor is shown for this period as Temperature.

    It would be better to see “- -“ or just see the last available temperature provided by Tempe.

  54. TSA

    how do you recognize a garmin fanboy?
    calling a poor engineering, subpair build testing processes
    and lousy mass production quality control “fascinating”…

    • How do you recognize a troll?

      Trying to be clever by changing their username and e-mail with as much creativity as a lonely piece of subpar parking lot gravel, while posting mostly similar comments with any actual substance or value on multiple posts. Of course, such rocks are rarely ever as clever as they thought, and are easily spotted as the troll comments they are.

      Cheers!

  55. Andy Large

    For me the bigger issue is buttons sticking due to saline water ingress. Have had that twice on Fenix 5 Plus. Never seen an official comment from Garmin on this but there is plenty of chatter about it in their forums, last time I looked.

  56. AlexW

    Man, that is absolutely THRILLING. Annoying to lose a feature (however useless) but super glad to find out there’s a very concrete and useful reason behind it.

    I’d LOVE to see the detailed failure mode analysis if you could convince them to blog about it! Tons of things jump to mind about the electrochemistry but I’d never in a million years have expected them to actually matter. It’d be early Christmas if you told me they had teardown/dissection photos.

  57. NataleeShields

    Thank you for this information, but I don’t understand why Garmin have removed the temp information from my app. I have a vivoactive 3 and use a paid app to record my open water swims. I noticed that the temperature had disappeared but thought it was a user error. I eventually tried to solve it today and came across this article. My problem is that the temperature has been removed front the swim results so I’m assuming that even if I but a Tempe I still won’t be able to see the results. I’m really frustrated by this. Any one tried this?

  58. David Jones

    I am currently on my 3rd F945. Yes, my 3rd!

    Garmin has replaced it each time, due to drift in the altimeter over time that I’ve experienced with each one….and I certainly used to do a lot of pool swimming. The attached xlsx shows the drift on the last one for the same commute on my bike, that resulted in Garmin giving me my 3rd free replacement (this took some effort, hence the spreadsheet).

    Why it seemed to take 6 months to start drifting each time now starts to make some sense, if it was related to wear of a component. If only Garmin had shared this with me all those months & years ago….

  59. Natalee Shields

    I bought myself the Tempe sensor, and it connects to my Vivoactive 3 watch ok. Went for a walk and was able to see the temperature on my watch fine. Annoyingly when I sync it with my Garmin connect app it does not show the temperature. They have removed this field from all activities recorded from my watch past and present, be it walking, swimming pool, open water, or cycling… I can still see temperatures in the Garmin connect app if using my edge 1000. When I contacted Garmin helpline they said yes it’s been disabled. No suggestion of how to resolve this. I’m still in a discussions but I’m especially annoyed that they have removed all previous temperature data.

  60. Andrew M

    Ray,

    It seems that Garmin have just reverse ferreted on the “pool chlorine causes barometer failures” issue.
    link to forums.garmin.com

  61. Sabine Wildevuur

    I am still looking for the open water watch that will suit me most. I really like to have a thermometer, specifically for the ice swims. However, reading the forums, specifications it seems that a sensor is hardly accurate in the watches. But I also carry an aquarium sensor with me. I do have an Apple watch that has at some times not been accurate at all with the GPS so I want to switch. But which one to choose if it needs to combine a thermometer and accurate GPS (Garmin Swim 2 will not do because of NO thermometer)….

  62. Andrew B Goetz

    Can I still get back in the water with my watch? Whether the temperature sensor is off or not chlorine will still affect it, right?

    I paid $578 (with RD Pod) back in 8 July 2019 for a fēnix® 5X Plus Sapphire that failed. Then around April 2021 additional $200 to have replace it, because of this issue with chlorine. I am starting to spend a lot of money on this issue. Will I be spending another $200 every year and half to 2 years?

    Random, but Humana Healthcare discounts are the best they gave me like almost $300 off my first purchase.