Beware Garmin customers that own, or are thinking about buying, any of the products containing the optical heart rate sensor.  I have now owned three Garmin products with the wrist-style sensor (Vivoactive HR, 735xt and the 935xt).  All of the devices displayed some level of this plastic warping defect.  Here is a picture of my older 735 with the defect.

The first watch I owned with an optical HR sensor was the Vivoactive HR.  After about six months it started to warp.  A month later the sensor failed to be able to read an accurate HR.  At the time I thought I must have dropped it or damaged it during use.  I then purchased the 735xt as both an upgrade and fix.

After three months with the 735, I noticed the issue with the new watch.  I watched over the course of the next 30 days as the warping got worse, to the point the sensor stopped reading.

Here is the biggest issue for Garmin consumers.  When I contacted them, they advised that the watch is only covered under a 90-day warranty.  I was about two week outside of that window.  I would have had to have paid $150 to obtain a new refurbished unit.

So, I then bought a 935, thinking the more sunk-in design of the sensor would fix the problem.  I purchased the 935 at the end of September 2017.  Today, at the end of March 2018, the watch is demonstrating the same sensor warping issued the other two watches did.  Here is what it looks like:

Garmin Forerunner 935xt with optical HR sensor warping.

I’ve again contacted Garmin about the problem on the third watch.  I was again told this issue is only covered under the limited 90-day warranty.

I’ve used each of the three watches as my everyday watch.  They are on my wrist 18 hours a day, 7 days per week.  Many times I wear the watch throughout the night as well.

I have no problem with this being an issue if Garmin would stand by their products.  I’m sure I am not the first person to experience this.   After three watches, all having the same issue, I’m confident it’s a design/cheap materials issue that Garmin is aware of but refusing to do right by their customers.

I love the functionality of Garmin products.  I’ve owned almost every Garmin GPS watch starting around 2000 with the old Forerunner 205 (I think that’s what it was).  I’ll fight with the company a little more, but if they decide to not stand by their product and replace this watch I’m done and will look to move over to Polar or Suunto.

I would love to hear if others have experienced this issue as well.



  1. I have had a Garmin 735XT for 1yr 4mth, and I really like that watch.
    Last week, during a swim, it stopped working. Upon closer inspection, I have noticed a crack over the OHR sensor, so I’m guessing humidity / water has sipped in.
    That crack cannot be a result of accidental damage, as I am wearing the watch all the time, except when it is charging once a week or so.
    I have not yet contacted Garmin about it, and I have been trying to see if this is an issue other users have had.

    • It is an issue that Garmin is aware of and they have opened a “case” with their engineering department. Contact their support via telephone and tell they what the issue is. They should replace the 735 with a totally now, not refurbished, unit absolutely free of charge regardless of how old the watch is. They did that for both my 935 and 735. If you get any push-back, contact me and I will provide you my RMA numbers. You can reference them and ask Garmin why they replaced my units without issue but not yours. But, I doubt they give you any issue.

      I’ve done some testing and I think the issue has to do with taking the watch between big temp changes, like from a cold pool to a hot tub. Curious if you swim a lot with your and if you happen to go from a hot tub to pool. And/or, do you live in a very hot area (I’m in Arizona) where the watch gets hot and then hits a cold pool.

  2. Thanks Brandon, I did contact Garmin and they accepted to replace the watch without any problem. I just had to provide a picture of the back. I’m waiting for the replacement to come through now.
    The problem happened while I was on holiday, so it may be related to what you suggested, as the weather conditions were different (warmer) to where I live, and the problem happened while I went swimming in an outdoor pool. Your theory seems to be relevant in my case.
    I wonder if they have addressed the issue or if I will need to be careful with the new device.


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