Fenix 6s pro, hr info not accurate when tracking activity.

My advice would be to contact Garmin Support before your warranty runs out. Then you have the fault recorded and can refer to that if you need to claim in future.

But for an immediate fix, which may or may not work, I recommend a hard reset (not a factory reset) by pressing and holding the Light button for > 15 seconds until the watch face goes black (off). Then restart the watch and see if anything improves.

Otherwise, especially if HR accuracy is important in demanding exercise, I'd recommend a chest strap. It's simply the better (best) way to improve accuracy. Wrist HR can vary from surprisingly good to pretty much junk. I prefer to remove the doubt.

Next step would be factory reset, which is probably what Garmin Support would advise, but I'd get that call logged just so you have some come-back.

We're discussing this in another thread - I have the same issue as you. I've tried lots of things (including having the watch replaced by Garmin, twice) to no avail.

try to wear your watch higher on your forearm. 

I have already tried that, thank you though! There's loads of things I have tried but it has become obvious the issue is software-related.

I am going to give you my 0.02. I do not think it is software. I think it is hardware. Some watches work, some do not. I got two 6S 3 years ago and whr was awful. I would go up and down the stairs to get my heart go up and it would flatline at 80. A bunch of weird stuff. I was told software would fix that but i returned them. A year later, i bought a 6 Pro. Did all the same test against a chest strap. I am anal about HR accuracy knowing the wrist limitation too. This time, the whr was close to perfect. The only thing it does not do good is weight lifting. I mostly cycle and use a chest strap but i wore the watch a little higher on the forearm and did some heavy power. The watch had a little lag but HR was close to perfect. I even did some test without starting an activity at the gym. Same thing. Watch has been great. The hrv overnight matches my whoop. When i had heart rate problems with my 6S, i had a friend that had none with his 6 pro doing the same test and running the same firmware. My speculation is that sensors may have different manufacturers.

Appreciate the info from all of you! I contacted support today and it was quickly agreed fro data review that there's an issue when comparing HR with elevation gain.

Did a hard reset with the CSR who asked me to try the watch for a few more activities and if no improvement, call back for warranty replacement. I don't need to be completely accurate with my HR, but expect a $700 watch to at least recognize when I'm exerting myself - like it used to....

SourCherry, sorry to hear this issue persists for you - I hope I'm not going to experience the same :-(

Hi Pierrotsc, it may well be that is is a hardware issue, but if it means anything I had a fully functioning Fenix 6 Pro which served me well for a year before this issue suddenly cropped up.

I am C+Ping my comment from the other tread for context re: what I have been facing:

 I have had the same issue now on 3 separate Garmin devices (a Fenix 6 Sapphire Pro, which Garmin replaced for me with a Fenix 6S Sapphire, which had the same issue, then was replaced with a second Fenix 6S Sapphire which *also* has the same problem.

I used to have great HR readings on my original Fenix 6 Pro watch up until August, when I noticed the HR reading just wouldn't increase when I was working out. I am usually on the treadmill, so I use the Treadmill activity, and that's where I noticed the watch was displaying an absurdly low HR reading in the middle of my workout. I ended up just using the Cardio activity as that was the only one displaying the right HR, but even that started malfunctioning after a few weeks.

As I said above, I've had that watch replaced, and the replacement watch replaced, because they all have the same issue. I have even tried using activities like Yoga and regular Running whilst running on the treadmill, and I know my HR should be 155-160, the activities always show 88-97 or thereabouts. It is only the Cardio activity that displays the correct HR, but from my experience with the first watch, even that malfunctions down the line.

I have tried all the different kinds of resets, I have moved my watch from one hand to the other, I have sent it in to the local Garmin distributor multiple times (I am not in the US or anywhere in Europe), I have rolled back the software (23.10 to 21.00) and absolutely nothing has worked. I imagine the chorus will jump in to say I should buy an HRM, but for what I've paid for this watch...no, I shouldn't. It was all fine and dandy until one day, it wasn't. And I see lots of reddit posts reporting the same issue so clearly this is a known bug that is not being addressed.

I have refrained from posting here or elsewhere because I was waiting for Garmin to do something about it, but it is clear the local Garmin folks (who in turn rely on Garmin Europe for advice) are unable to help and folks in the US aren't able to address this either. It is very disappointing as the HR reading is what tracks calorie burn, and while we all know it isn't medically accurate, that is the information I need to maintain my weight goals.

Since posting this I have, as suggested by some lovely users, also created a new Connect account, factory reset the watch, and connected the reset watch to a new account to see if the phone/my account was the issue. I still saw the HR errors come up. 

SourCherry, thank you for your details - it has helped me do some investigating on my end. My 'Track Me' HR stopped working properly btwn my Aug 31st activity (HR worked) and then the next Sept 14th activity (HR didn't work properly). My hikes used to be 'threshold', but since Sept 14th every hike/activity has been 'Base'. Recovery times used to be a couple days and now it reports 4 to 8 hours!

1. Today I went for a walk and decided to test the 'walk' activity tracking instead of the 'track me' setting. Guess what, HR readings were like they used to be. I would start climbing up a hill and my HR went to 140 pretty quick. I stopped the activity and changed it over to track me and went up the same hill again, as I was climbing the hill my HR went down instead of up!? So I again decided to stop the track me activity and flipped it back over to walk activity and went back up the same hill and yep, my HR went right back up again. I did one more test flipping it back to track me and did the same hill one last time and yet again the HR decreased as I exerted myself up the hill. 

Now this was just a very short duration test, it will be interesting to use the 'hike' activity for when I'm in the backcountry for hours and doing substantial  elevation gain.

You said that you also had success with switching over to specific activity tracking but then shortly after the HR failed this way as well?

Hi Chucky80, no worries at all and I'm sorry you are facing the same issue. 

Yeah so I mainly use Treadmill and that's what's been malfunctioning this whole time, but over the last few months I've also tested Yoga, Strength, and Running on all 3 watches and those give me incorrect HR readings too. Back in July, when I was on the treadmill, using the Treadmill activity, I used to get readings of 145-170 based on how much I was pushing myself - now it is usually in the 80s or 90s and, like you, tends to decrease even though I am pushing myself harder.

And yes, for my original watch, I switched to Cardio for a few weeks when I realized all the other activities were giving me the incorrect HRreading, but after a while the Cardio activity ended up having the same problem. I am currently on my second replacement watch and haven't had the opportunity to keep tracking Cardio as much but as with the previous 2 watches, every other activity gives me low HR readings.

Funnily enough, sometimes if I start with Cardio, and keep the HR tracked there for a bit, then switch to Treadmill, Treadmill shows me the right HR for a while before it goes on the fritz again.

I posted these in the other thread - this is me after 20 minutes of running on the treadmill. The HR is so low and so erratic (and obviously incorrect):

Whilst on the treadmill, I switch to the Cardio activity after stopping and saving the earlier Treadmill activity. This is displaying the right HR readings: