Electronic Compass is not reliable

[MarkHL]

The GPSMAP 66s is the 8th handheld I've purchased from Garmin. Currently, I'm using a Oregon 600 and Etrex 30x. I possessed the 66s for 26 hours before sending it back due to the electronic compass inconsistencies. I had the heading setup for numerical display.
I could not trust the reading. Sometimes it appeared correct, other times it was off by 20+ degrees off (e.g., reading 66 degrees instead of a known bearing of 87). My other two handhelds had no issues with showing the heading.

Is this typical of this model or did I just get a bad unit? I was using firmware version 3.40 and calibrated the compass away from interference's. If I thought it was a faulty unit, I'd order another one, but currently, I'm a bit disillusioned with this model even though there were many things I liked about it.

[GPSrChive]

Not typical.

Did you have heading configured for true north, magnetic north or user specified magnetic declination?

Sending it back only 26 hours after receiving it - hardly enough time to get acquainted.

[MarkHL]

True north which would compensate for the 15.41E declination at my location.
8th unit I purchased from Garmin over the last twenty-years, "acquainted" is not the issue.

[GPSrChive]

I do not recall ever having any issues with the heading display with either of my GPSMAP 66 units, but now that you have brought it up I will pay closer attention my next time out and I'll be sure to take a couple other units with me for comparison.

[MarkHL]

A more detailed explanation of the issue I was having. There are points across the water that I am familiar with the bearings from my house. I've used them to verify how accurate I can point a Suunto MC-2 compass. I rarely miss by two degrees with an actual compass. Most of the time I'm dead on. I use the same locations to test the accuracy of the GPS electronic compasses. No issues with the Oregon 600 or Extrex 30x giving me the correct numeric heading.

So after calibrating the 66s (repeatedly), I point it at a known 115° bearing and it reads back 115 degrees. I then rotate to a known 87° bearing and it jumps to 66° and never corrects itself. The other two GPS's have no issues of smoothly going back and forth between the 115 and 87 degree reading.

Think of kayak navigarion on water if you need to visualize why I use the gps in this manner.

I wonder if it's a faulty unit or this behavior is typical of the design of the magnetometer in this unit. Since the 66s is currently in sale, I'd purchase another one if I thought my unit was faulty.

[GPSrChive]

The only truly conclusive test would be to get another GPSMAP 66 and perform the same test and report your findings here. We can address the results when we have them...

[MarkHL]

Second unit was delivered today and the electronic compass functions correctly. Smoothly and accurately moving between headings.

[GPSrChive]

Excellent! Thank you for the update!