Outside mirror, driver's side
 

My heated mirror doesn't want to work anymore. The passenger side works like a dream, same with the rear defroster. I assume that the driver's mirror is on the same circuit as the passenger so I'm ruling out fuse. Is there a replacement for this? If so, where and how do I get the mirror out? I looked in the manual and it says to "pull" it out, but I'm a little concerned about breaking it...

Hi there, I've read something on this before, it could be a broken wire to the heater, or a broken heater in general, you can test the wires to see if they're getting power, but i know its scary to pull the mirror out, but I'm thinking it's a heater gone bad and if you're really worried might be best to get a new one, or buy one on ebay used or hit the wrecker it'll need at the worst to be painted. Try to see what you can do, if it's too risky buy the whole thing.

Also, depending on where you live i have an extra one if needed from an S70 this one wasn't as cheap as what i used for my 850 but its from a black S70 so let me know how things go. :)

Most likely a bad heating element in the mirror.

Okay... I want to test for voltage at the mirror to see if the element is bad. How do I pull the mirror to do this without shattering it?

The mirror clips in on three clips. i think could be more, pull it or adjust it all the way to one side to reveal as much of the back or inside as possible.
One of these clips is the pivot and the other two are up and down. The new mirror simply snaps back in place. I would get WD40 to lubricate the snap points since you do not want to crack the plastic. or any spray lubricant safe for plastics. Since your mirrors are heated you will need to disconnect the wires once the mirror is out, and then check the power there, but it's most likely damaged/broken if the other side works, plus defroster. Disconnect the heating element and try to replace it, if you can't locate an 850 one, any Volvo heater for that size mirror should splice in, just watch the voltage to make sure its not over doing it :)

Good luck, let me know.