Heated Mirror

[SVX ROO]

On first cool morning I noticed that the left hand mirror heater was not working on my ’94 SVX. I suspect something inside the mirror since the right side is working fine. I looked at the mirror and I can not figure how to take it apart to get into the heater. All I see is three Phillips head screws that remove the whole assembly from the car and those screws are near impossible to get to.

Is there a way to pop off the black frame behind the mirror or separate it from the painted part? Any ideas, please let me know.
Thanks
Ken