A few days ago I noticed my compass and temperature display were not working. I tried to hold the temp button for 5+ sec so that the green light went off and then switched it back on but had no luck with that. I also googled that the mirror was sharing a fuse with the cruise control which is working fine and my guess would be that if the green light is working on the mirror so was the fuse. A replacement is relatively cheap (about 25$ for a used one) but before I bought it I wanted to get a second opinion from you guys.

 

If the light is on the fuse must be good. I bet you are correct in the assumption that the mirror is faulty.

 

I know I'm posting to an old thread, but what the heck... Last week my mirror's compass/temp has all the LED segments on. Similar to this picture. Obviously it has power so I'm assuming some internal failure.
Although I'm almost sure it looks like this when the truck is started and then goes into normal display mode.
Is there an easy replacement?
Compass isn't really any big deal but I always look at the temp.
Thanks!

 

03-09 Hummer H2 Auto Dimming Rear View Mirror

 

It's not easy finding data on the inside rearview mirror internals and personally never seen one up close.

I found about GM Compass Mirrors, its not the same, but the H2 mirror may be similar and it might provide a clue as to what could be wrong.

 

my 03 H2 mirror has done the same recently. honestly I dont care about the temp or direction. But, I need the auto darkening feature. green light is on but no temp or compass. probably going to go for a new used one