Garmin Fenix 8 - Not recording external HRM correctly

Hey, what activity do you use the HRM at? Did you try to turn the dynamic HR source off in F8?

If you remember which activity is it and if you wore the watch during that activity, export it, open it at fitfileviewer.com, click on "chart" and choose "wrist heart rate" on y1 axis and "external heart rate" on y2 axis. There you can compare what F8 measured on optical HR to Wahoo HRM. Are the measurements too different at some point or are they nearly the same all the time?

Thanks for the response. So to be clear the fenix 8 says it is taking the data from the Wahoo. But the numbers made no sense.

Activity was running. I will try to get this data for you.

What is the dynamic HR source?

7731073 said:

What is the dynamic HR source?

Search for Dynamic Source Switching in the user manual. 

It does not have to be true that F8 takes data from external HRM. It usually combines the data from OHR and HRM. That's Dynamic Source Switching. Try to look at the graph at fitfileviewer.com, you'll see. Ideally show us screenshot of the graph.

I should point out the external heart rate is almost certainly correct and in line with previous workouts. 

And now look at "heart rate" graph, that's mix of both which Garmin shows you in the activity. 

Watch apparently does not keep up with fast HR changes. Do you wear them snug fit during workout? Do you have any tattoos or dark skin? That can affect ability of reading HR optically.

The best for you will be to turn off Dynamic Source Switching, so watch takes HR from your chest strap as main source of HR during workout.

I have the same problem, do you resolve it?

But how I turn it off the dynamic HR source?