Heartrate way off - Anyone with the same problem?

This is quite a common syptom when starting a workout in cold weather without a warm-up. Potential solutions:
1. Wear the watch tighter.
2. Do a warm-up before starting an activity.
3. Use a chest strap.

Thanks for your answer, but
1. i can not wear the watch any tighter
2. even when i warm up, like yesterday, the hearth rate needed 35 min to adjust!
3. i bought a really expensive watch for the reason, not to waear a chest strap or buy one additionally.

i already thought maybe its the cold weather, but yesterday was a quite warm day and like i said, it didn´t work out at all. i am running like crazy and the watch tells me i have a heart rate of 152 - unrealistic with a max of 195. also - the problem first occured last year when it was still end of summer.

is there no way this could be a software problem? or hardware?

I'd rather rule out software issues. I've been using the 735xt for over 2 years, and sometimes I, too, experience similar symptoms, but I can almost always attribute them to cold and dry weather, and in my case it usually needs 10-15 minutes to catch up, not half an hour.

There's not much further advice I can give you. Optical sensors often do not work well in high-intensity exercises. Anyone who requires reliable heart rate data should consider a chest strap.

One more tip:
Inspect the underside of the watch. Look closely at the glass covering the optical sensor. Look for scratches or even cracks. Make sure it is clean.

I noticed the same during my last runs in cold conditions. HR 20 beats too low. Wearing it tighter isn't a solution, although my wrist is a bit thinner in the cold. But during activity, after a shower or something else that lets the blood flow into the hand ist would be too tight, I already feel that by moving my hand and wrist. I had runs with HR too low during the whole run, runs with HR suddenly increas after 20 minutes, runs with suddenly decrease HR after 20 minutes, runs with HR near max HR although it was and slow run and I didn't feel exhausted or tired after finishing. Now I bought the HRM Run. I wanted it for running dynamics, obviously I should use it for HR too. When my cold is gone I'll continue running and test it. My FR235 that I had before wasn't way off in cold conditions. But the FR735... Meanwhile it seems to be way off all the time. RHR doesn't decrease anymore although it was a light cold, stairs or walking faster lets the HR rise to anywhere. On Friday I'll ask my doctor if he is really sure that my heart is fine and if he still doesn't want to do an ECG that I already requested in January after overstraining during a 10k after another infection.

First of all: Get well soon Carmen!
Yesterday i orderd the HRM Tri and i will report how it works.

The HRM Tri works fine!
But i can report an update on the Heartrate problem:
Yesterday i went hiking, did not wear the HRM. After almost an hour i observed, that my heartrate is again way off. it was maybe around 2 Degrees Celsius. I covered the watch with my hand to warm it up, and it got back to the normal heartrate. After removing my hand, it went back to the wrong heartrate (40 beats too low) after maybe 1-2 min. So i detected, thats this is a problem when its cold. For the rest of the activity i put my sleeve over it, so it measured right but i could not obsere it the whole time.

Is it a known Garmin Problem? Or is my watch just broken kind of?
I mean, what sense does it make to buy a very expensive Garmin Watch, when i can not use it when its cold? If i would move to a cold country, or live in alaska i dont know, i would not be able to use this watch with my heart rate at my wrist.

Obviously it's a 735 problem. I didn't have these problems with my 235 last winter. Now I use my 735 with the HRM Run. It reads higher with the strap. Maybe the readings with oHR were always too low. I'll observe it, maybe I'll have to change maxHR. All other things the cardiologist will tell me. Meanwhile I'm nut sure anymore if my 735 hasn't any problems. On Friday afternoon after a run I sat at the doctor and the watch told me that my HR was 35! Well, it rather felt like something between 80 and 90. After a few moments it showed 85. The graph showed 0 and something up to 30 for the last 45 minutes. Strange. The strap was at home. Less than 6 months old and broken?

When your skin is cold your body restricts blood flow to it to prevent heat loss and protect your core temperature. Optical HR sensors rely on blood flow in and just under the skin so they struggle when it is cold. It is unfortunately just a limitation of optical HR sensors.

You could try wearing the watch a bit higher up and on the inside of your arm where there is a bit more flesh. I have had much better HR data doing that in the past compared to wearing it in the normal location.