Are you moistening the contacts on the HRM before you put it on?

I found chest strap based HRMs need that otherwise the readings can be totally unreliable. They also need to be quite snug, atleast for running.

It got to be quite a pain so I switched to wrist based after my last chest strap died.

I don't have Garmin / Garmin accessory experience, but with both Polar and Suunto, I have found that erratic, extreme or volatile HR readings are a result of a bad / worn chest strap (specifically when the pads on the strap seem like they are peeling off).

Previous recommendations of ensuring the right fit and moisture / contact gel are in my experience legitimate as well. Although, i have found that if I actually wear it too tightly, the readings seem to be junk too.

That. Or moisten the skin.

Dry HRM chest strap gives erratic readings. Especially with synthetic clothes on. Workout sweat makes great conductor, so this problem largely goes away when you get going (5-10 minutes into a workout). Exception is outside on cold days when you don't sweat as much, and on top of that the wind can dry out your clothes, skin, and HRM, thereby reintroducing this problem even after you've moistened everything before the workout.

I had the same issue with the same Garmin V2 HRM when I first bought it. The first 5-10 minutes were erratic and usually too high. I started moistening the contact area with a dab of liquid hand soap or shampoo (whatever gel-like substance I happened to have nearby) and the problem went away. Two years and a few batteries later, and the same HRM is still going strong.

Sometimes HR monitors just plain give crazy results. 10yrs ago my HR was way too high for a couple runs. I got a little spooked so I made an appt with a cardiac specialist to do a stress test. Turned out that the problem was the HR monitor, a high end Polar unit, misbehaving. Every couple of months, over the last several years and encompassing many HR monitors, my HR will read goofy high. That cardiac stress test taught me to ignore the goofy results as spurious.

Not all problems make sense or ever really get figured out. Sometimes problems go away on their own.

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i own a 935 and that same hrm wristband. i suggest you follow previous advice posted here and if nothings works i would think about a defective cheststrap. Sometimes my cheststrap does not work properly on the first 10 mn but after that everything ok. after i moved to contact gel i have enver had problems again.

If you see these types of numbers after fooling with the strap, battery, different monitor, etc. go see your doctor. Takes just a few minutes to have your heart tested with an EKG.

It is freaky to see 195 ave bps for a long ride or run...there is a reason.

Message me if its not equipment related.

Take your pulse and see how closely it correlates.

I had this issue also. Bought a new HR strap. I still got crazy numbers which I "knew" could not be correct. Went to Walmart and had the BP machine check my BP and pulse for free. It showed a crazy number for my HR. Went to Dr. Sure enough I was in a pretty severe case of A-fib. If I remember my HR was 180-200 bpm just walking across the room. My normal resting HR of 40 bpm was double.

Hopefully it is just a case of malfunctioning equipment.