Fixing the Altimeter on my Garmin Forerunner 910XT

As many of you may know, I’ve had numerous problems with the altimeter on my Forerunner 910XT. Since lusting after the Forerunner 910XT back in October 2011, I bought one in February 2012. I then wrote a glowing report on the Forerunner 910XT with my first impressions  – it did just about everything I wanted it to do, and did it well.

Everything seemed to be working well with it, except for one little hiccup when it produced a strange route a month or so later, but other than that it seemed fine. I used it pretty much everyday for all of my swimming, biking and running sessions, I used it in the gym and on my turbo trainer and recorded all of my training with it. It synced with my computer via Garmin ANT+ Agent software and from there to the various software that I use to track and analyse my training.

That was the way it was, me and my Garmin Forerunner 910XT spending far too much time together, sweaty, puffing and panting. Then in July 2012, after about 5 months use the altimeter stopped working. One day the elevation just suddenly jumped and then had me at close to 63,000ft all the time. Garmin were contacted and a returns number was issued. I paid for the postage to send it back and I soon has a replacement unit under warranty. Garmin’s warranty service was good and the new unit was functioning well.

Then in another 5-6 months the same happened again. the altimeter went hay-wire and ended up recording that I was at 63,000 feet and there were no ups and downs in my life. Once again I was without my (now not so) trusty Forerunner 910XT whilst it was sent back for replacement. Once again it cost me to send it back too. I was also now a little worried that the warranty would have expired if this happened again, so got Garmin to extend the warranty for me just in case.

Sure enough, in another 5-6 months, now July 2013 the altimeter did it’s thing and I had to call on the warranty replacement services of Garmin yet again. I had suggested that they simply make it possible to turn off the barometric altimeter within the settings on the watch as there was clearly an issue with it. Most people, myself included would be more than happy not to have a barometric altimeter. With no altimeter we could simply rely on GPS map data for the elevation readings once the workouts were downloaded to the computer. This didn’t happen of course but it seemed like a simple solution to me.

I was now onto my 4th Garmin Forerunner 910XT and was getting quite used to the warranty replacement service. I think I know the returns address off by heart as I seemed to be using it every 6 months, and sure enough, 6 months down the line in December 2013 I was using it again and was now onto my 5th watch from Garmin.

A friend of mine, Michael who was having similar issues with his 910XT then directed me to a forum post on Fast Twitch where some people were reporting that they had had some success with barometric altimeter issue simply by giving the two little holes in the back of the device a really good clean with hot soapy water and a toothbrush.

earlier this year my original 910xt (watch #1) stopped recording elevation correctly (as stated above). I got a warranty return and got a replacement (watch #2), which unfortunately had a very sticky button and was promptly returned. Watch #3 worked great for a month then elevations stopped working again. I swim daily, bike and run frequently…

I emailed Garmin and was about to send it back, before I came up with the idea to WASH MY 910XT. I put it in a warm water soapy bowl, and using a clean/unused toothbrush brushed the two barometer vent holes. And… it worked (recorded elevation changes) again! I recommend cleaning, it might be sweat, chlorine, river scum, sunscreen.. but that will be my first approach next time this happens.

I kept this in mind ready for the next time mine started acting up.

Sure enough, last week the barometric altimeter issue on the Garmin Forerunner 910XT once again reared it’s ugly head. The watch stopped recording elevation correctly and had the altitude I was at flat-line at around 3900m – In reality I was actually a lot closer to sea level than that!

So, out came an old toothbrush and I gave the barometric sensor holes on the 910XT a really good scrub with hot soapy water. I then let them dry out before turning on the watch to see what elevation I was at. Sure enough, it seemed to do the trick. At home the watch was recording that I was at close to sea level.

I then went out for a run which involved hill reps – the perfect test for an altimeter and I’m pleased to report that it was working a treat. The run consisted of 5x 3 minute hill reps on the Caer Gybi hill just outside of Machynlleth. A 3 minute climb here only takes me halfway up the hill, but there was already a Strava segment up to this point on the climb so I did that 4 times and then finished off with a longer 6 minute climb right to the top.

As you can see, the altimeter seemed to work flawlessy, reporting 4 even ‘ups’, 4 even ‘downs’ and then a longer ‘up’ to the top of the hill. Hooray, there were ups and downs in my data again! Better still, I also got the Course Record on the Strava segment here and also posted the 2nd, 3rd and 4th fastest times ever on the segment too. Success all round – The altimeter on my Garmin Forerunner 910XT seems to have been fixed by giving it a simple wash, and my training session was a good one.

Hopefully the altimeter will continue to work and next time it starts playing up a wash will do the trick. If not, it’ll be going back to Garmin again but it does seem to have helped this time so far.

Quite why Garmin have never suggested this simple procedure to me I don’t know. I doesn’t seem as though asking people to wash their device and to make sure the sensor holes are free from grime would be too much to ask. After all, when you think about it it is quite likely that these little holes would clog up over time considering the things we put these watches through. If this really has solved the issue then Garmin could save a lot of wasted time, effort and money by asking people to wash their watches before offering replacements under warranty. I’m sure they should have worked this out as being the problem by now as surely they must examine the returned devices to work out what has been going wrong with them?

I think I shall have to ‘pen a letter’ to Garmin – or at least fire off an email with a link to this blog post. In the meantime, I hope this little trick helps you with any problems you face with the barometric altimeter on your Garmin Forerunner 910XT. Please post in the comments to let me know if this has or hasn’t worked for you as it would be good to know if this is really the problem or if I was just lucky this time.

32 Responses

  1. Avatar forComment Author GLawton says:

    Took your advice and a quick soapy wash has left me with a working alimeter and accurate elevation readings again. It was interesting to see that when I turned the 910XT on again after it had dried out, the elevation started at 9000m (I live at 200m)and slowly dropped by 200m at a time to the correct level. Weird to see. THe only other thing i will note is my elevation readings started going haywire after I started open water swimming. Might be a coincidence? Thanks for the insight – very happy with the 910XT again!!

  2. Avatar forComment Author SoCal Darwinism says:

    A note of caution; the first time I tried this fix I might have inadvertently ruined the device. I assume that inside these small ports are thin flexible diaphragms, acting as ‘ear drums’ for pressure. If you scrub the small ports too vigorously or too deeply the ear drum can be punctured and the water proof seal compromised. I suspect this is why Garmin does not publicize this ‘fix’.

    I am on watch #2, it lasted ~4 months before elevation malfunction (1st one lasted ~10 months). To date one gentle washing has not fixed it. I plan to try again, but am gun-shy from my previous experience.

    The 910XT is my most prized possession, its data motivates me onward and upward (despite lack of elevation data!). Frustrating bug, and poor response from Garmin, but not a deal breaker for me.

    Thanks for your useful post!

  3. Avatar forComment Author doubleM says:

    Great post. I got the same issue and after washing my 910XT twice the device has been able to give correct elevation again. I hope not to have damaged the device anyway. Actually I am pretty sure that when it used to work it was able to show elevation data even when GPS was disabled.Now if I turn off GPS elevation data are not shown ….
    No answer from garmin support so far.

  4. Avatar forComment Author Jerry says:

    Thanks for the great advice. My altimeter hadn’t been working for a few months and I missed the feedback. I washed the watch in warm water, and used the toothbrush to give it a good cleaning. After it dried out, it found the right elevation and it tracked it correctly throughout my ride.

    It’s amazing Garmin hasn’t offered this simple and effective advice.

  5. Avatar forComment Author Xavier says:

    Having the same issue, thanks, will try the advice. However, I upload all my data to Strava where you can do an elevation correction based on the map and the route you have taken. That also works very well to analyse my data afterwards.

  6. Avatar forComment Author Andrea Rafael says:

    Hi – I have a different issue: battery loses power too quickly and the alerts don’t work (swim or run distance alert) – the unit does not vibrate etc.

    Any experience with this?

    • Avatar forComment Author Alan says:

      Sorry Andrea, I haven’t heard of this issue before… It might be worth looking on the Garmin Forums, or better still contacting Garmin Support – They have always been very helpful with me, and if the watch is in warranty I’m sure they’ll replace it for you.

      Good luck, and let us know how you get on.

  7. Avatar forComment Author Brian Wright says:

    This actually works. I’m on my second Garmin 910xt.1st one last approx 6 months and the same for the second. I used dish washing liquid ( I’m in the UK so I used the Fairy Liquid brand ). I let the water run hot from the tap and let the watch soak for about 30mins. Gave good it a scrub with a toothbrush as described in this post making sure to get right into the 2 sensor holes with the brush bristles. Let it dry for a bit and turned it on outside to let it get a salatite reading. When it turned on, the elevation reading showed “—–” and then the saltilte search screen inititated. It took about 15 minutes outside before it registered all 5 bars. Checked the elevation reading and it was spot on!

    • Avatar forComment Author Alan says:

      Glad it worked for you too Brian… I’m in the UK but used Morrisons Own brand washing up liquid! I’m still puzzled as to why Garmin keep sending out replacements without even asking customer to give this a go go first.


  8. Avatar forComment Author Ido says:

    Your advice was very helpfull. It fixed my Garmin 🙂

  9. Avatar forComment Author Ruffles says:


    Just a quick technical note. The reason Garmin fit an altimeter is that GPS isn’t great for altitude. (Apparently this is because the best satellites to use are hidden by the earth’s surface). I have an old GPS on a boat that often reads 100′ above sea level – at sea.

    So Garmin use the barometer for fine altitude readings and the average GPS reading to normalise for atmospheric pressure. Which is great – when it works…


  10. Avatar forComment Author ClickyPaws says:

    Thanks so much for posting this. Just cleaning didn’t work for me (did it a couple times), but after a third attempt, plus some other steps, the elevation appears to be working! Here’s what I did the third time around:

    1) Checked to see if my barometer is faulty (see steps at the bottom of the post below)
    2) Turned off watch
    3) Soaked in dish soap & warm water for 30 minutes
    4) Scrubbed with a toothbrush
    5) Rinsed the device with clear water
    6) Blew out the barometer holes using compressed canned air (the kind you use for blowing dust out of electronics)
    7) Set in sunlight for an hour to completely dry
    8) Did a master reset on my device (see instructions from Garmin below, upload your data first – this erases it)
    9) And voila! the elevation is no longer 65000 feet. It’s showing a good approximation (350 ft) of the elevation I live at.

    I need to get it out for a couple of workouts to test it out further, but it looks promising. Thanks again for helping me fix my watch without having to go through Garmin support!!

    Instructions to check for faulty barometer

    ( posted on the slowtwitch site:

    A random number of 910XTs have faulty barometers in them. There doesn’t appear to be a pattern of serial numbers affected. To determine if your barometer is faulty. go in to the diagnostics mode:

    1. Power off the 910XT
    2. While first pressing and holding down the Enter button, press and hold the Power button.
    3. Continue to hold both the Enter key and Power button until the diagnostic screen appears.
    4. Release both buttons.
    5. Now that you are in the diagnostic screen, press the Mode button, exactly 7 times. (The 910XT should beep each time the Mode button is pressed.)
    6. Check the third line called “Baro Alt”, if it shows 65,000 ft or 20.00 m and the fourth line under “Baro Pressure” shows 0, then your unit is faulty.
    7. Power off the 910XT to exit out of diagnostics mode.
    8. Call Garmin for help if it’s faulty

    To Perform a Master Reset (you will lose all of your data, so be sure to download it first):


    Power Forerunner off
    Press and hold Mode and Enter buttons
    Press and release Power button (still holding Mode and Enter)
    Release Mode and Enter once Power is released
    The reset on the Forerunner 910XT is successful if the device finishes powering up and goes to the setup wizard. Try the steps again if the setup wizard does not appear.

    Leave the device outside with a clear view of the sky for a minimum of 20 minutes to acquire satellite data once the reset and setup wizard are complete.

  11. Avatar forComment Author Ivan Sinigaglia says:

    Thank you very much. This procedure fixed my 910XT altimeter issues.

  12. Avatar forComment Author Number 2 says:

    Thanks for the tips – I had tried scrubbing the barometer holes before, but not a full reset… giving it a good old soak, scrub and reset did the trick!

    I use my altimeter in the hills for navigation and thought I was going to have to invest in new watch (would the 920xt have the same issues???!). But now I don’t have to – Awesome!

    • Avatar forComment Author Alan says:

      I’m not sure about the 920XT but I imagine it has similar holes that might need cleaning out from time to time. My new Fenix 3 such holes that are smaller than those on the 910XT so no doubt they’ll need a scrub at some point. I haven’t heard of any such issues with these newer watches yet though, but I guess that could just be because they are too new to have got clogged up yet.


  13. Avatar forComment Author Dan says:

    This worked like a charm for me. I was baffled until I saw your post, and since I also was getting reading of altitude over 60K I knew we were having the same problem. Thanks so much. I’m going to share with the Tri team I’m on.


  14. Avatar forComment Author Amy says:

    Is it normal during the 20 minute period where you leave the watch outside after the reset for the elevation to go down but then jump up to 65k and then start going down again from there to finally arrive at the correct elevation? Or do I need to try to do the hard reset again?

    • Avatar forComment Author Alan Cole says:

      Not sure I know the answer to that one, but a reset doesn’t do any harm and then I’d just leave it to see how it is after that. If the readings are OK then I wouldn’t worry.


      • Avatar forComment Author Amy says:

        Thank you – I had just done a hard reset so I was concerned that it didn’t fix the problem and that a second reset might be necessary. Or maybe the elevation jumping around during the 20 minute period is normal and I just need to wait. I’ve just never seen it do that before.

        • Avatar forComment Author Anonymous says:

          Mine is doing the exact same thing.
          After cleaning and scrubbing last night and leaving to dry, the altitude dropped from 20,000m to about 17,000m. I left it on for a few hours last night and it did eventually find our elevation (about1090m). Turning the device in this morning however I was back to 17000m. I just did the reset and the numbers are up and down between 1000-18000m.
          If this doesn’t work, I a,y try cleaning again before calling Garmin.

          • Avatar forComment Author Alan Cole says:

            I hope the second cleaning works for you as it’s certainly a lot less hassle than having to send it back to Garmin, although the turnaround time on replacements were pretty quick for me.


  15. Avatar forComment Author Alejandro Guzman says:

    Excellent!! Fixed my Fenix 3!! Thank you

  16. Avatar forComment Author LizDunlop says:

    Just tried this on my 920xt.. and it has also worked.. wish I knew about this at the start of the year when my elevation went sky high.. just been making do and correcting it in strava.
    Washed it out with soapy water and a brush and dried overnight.
    Elevation is normal again..

  17. Avatar forComment Author jstreetley says:

    Just giving mine a good soak in soapy water now after noticing my elevation was appearing as 65516 ft for the last few rides. Thanks for the top tips – I hope to report a success story tomorrow.

  18. Avatar forComment Author Mark says:


    I’ve just followed the process above – I didn’t have the patience to wait for the sun to come out so I used a hairdryer. I didn’t reset the watch either and the elevation is counting down from 20k. I’ll post back if it works on my next bike ride.

    Thanks for the tip, really appreciate you sharing.

  19. Avatar forComment Author Brian says:

    Hi Thanks for the information. I have just tried this as well and found that so far it appears to have worked. At least it now no longer appears that I am carrying out my runs somewhere up in the stratosphere

  20. Avatar forComment Author Justin says:

    Think I can positively confirm that this error is probably more likely than not a clogged port most of the time. Have a Fenix 3HR and knew of this issue but hadn’t experienced it in my 7 months of ownership, probably because I al ost never take it off, I use a nylon strap so I bathe with it on to also keep the strap from stinking and thusly likely cleaning the ports as a result. Today I applied sunblock on my arms on a hike and the next thing I knew I was at 65K. I reset several times and manually set elevation, no dice. Suspected a clogged port and tried to clean it out by water bottle and admittedly swishing the water on it with my mouth as well as some vacuum from sucking on the port. This changed the error, now I was trending at -3K. Gave up and finished the hike and washed it with handsoap and warm water on the ports, no toothbrush, for a couple minutes, and it’s been back to normal and stable for 8 hours.
    Thanks for running this site, I agree that it’s crazy that Garmin is footing the bill for all these returns if a little bath is all it needs!

  21. Avatar forComment Author bixGiallo says:

    Thanks a lot for this trick. It seems that my Garmin 310XT now is correctly tracking the altitude. I run twice the cleaning following the advices of ClickyPaws too and for now everything is fine.
    Thanks to all comments and replies because I learnt a lot about the altimeter issue and more.

  22. I had the same problem on my Forerunner 935. Applied the warranty once, but the replacement had the same issue.

    After cleaning using hot water, soap and a toothbrush the altimeter was fixed. It was magic.

    I have had this problem for months and now it’s gone with a simple clean. Thank you very much!

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Alan Cole

Alan is a Freelance Website Designer, Sports & Exercise Science Lab Technician and full time Dad & husband with far too many hobbies: Triathlete, Swimming, Cycling, Running, MTBing, Surfing, Windsurfing, SUPing, Gardening, Photography.... The list goes on.

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