Wrist heart rate monitor WHR inaccurate

I have been experiencing the same issues - I am on 2.8 - but it was pretty erratic before on previous firmware levels as well. I will be exercising on my bike and all of the sudden it will drop from say around 120-130 to like 90 and stay there for some period of time. At first I thought it was real and there was something wrong with me - but I decided to wear a chest strap to compare and it can often be as much as 25-30 bpm off or more. Not at all dependable or accurate. And I am not wearing it loose at all - in fact my watch isn't moving around at all on my wrist during the workout - so not sure what else I can do to try to get it to be more consistent.

This picture was taken on the flats. As you can see, not that fast but says i have 196 HR. There are definitely big issues with 945. Will call support and ask about refund next week.

Looks like you have it on very tight? Tried loosening it up 1 notch?

Having the same issues.  My Fitbit Ionic was more accurate than this (but of course it broke).  I bought a Galaxy Active2 and had the same HR issue.  I want to stay away from chest straps as I have issues with those and is the reason why I bought this.  Pretty disappointing, but this does only happen when I'm not active.  But for $600, it should always work!  Any fix?  I guess I'll call support.

No fix. It's become completely useless over the past few updates (since 2.5 - and always getting worse).  My rest reading is 20-30 beats higher, and workout activity is always a random number.  I bought a chest strap too.  So I can verify my HR is 120-130 normally and not 160-180 as reported.   

Having the same issues on my 645 (I know this is a 945 forum). The WHR seemed fine a few months ago. The at rest WHR is reading 20-30 bpm too high. I check my HR with a handheld ECG, and also by just old school counting beats for 15 seconds. 

I'm on the latest software update. When I wear the chest strap, the readings are as expected.

From a run this morning with a Marq Athlete on the left wrist, 945 on the right wrist, both WHR. I'm happy with this.

Far from getting worse, in my experience there's been huge strides made in WHR performance over the years.  And I've been very sceptical in the past about it's utility.

It's weird, my heart rate monitor has been quite accurate lately. No more spikes. Prior to this I would only get accurate readings while in an activity. Someone posted that the heart monitor increases it sensitivity during an activity.

What might of helped was that I set the HR monitor to be always on. There are other settings to check your hr in certain intervals, which to me can throw off the readings.  Though I forget where that setting was at.  Doesn't really drain too much battery imo. Hope this helps. 

Not necessarily. WHR works for some doesn't for others. Works for some sometimes (me included) and doesn't work other times. Search online, read the information presented numerous time in the too many to count threads that keep posting the same thing time after time. WHR is not perfect, is unlikely to be perfect, but it is getting better. Just because yours is giving you bad information does not mean it's a dud. Check everything that's recommended/suggested. In the end, if you want almost guaranteed reliability, use a strap.

But of course, if you really think you have a problem watch, talk to Garmin.