The driver's side door mirror isn't defrosting (passenger is fine) and I want to check whether it is getting any power to it.

I had hoped to adjust it enough so that I could get the probes of the tester in, but there is not enough room, so need to remove the glass.

Someone had previously tried to help themselves to my passenger side mirror glass, breaking a couple of the clips in the process, so it is now clipped/stuck in position.

Is there a knack to removing the glass, as don't want to break the clips on the driver's side.

TIA