Heated mirror on 02 Avalanche

https://www.autoandtruckmirrorsunlimited.com/product/00-05-buick-lesabre-driver-side-mirror-replacement-heated-with-memory

Look in the fuse box for the fuse it will likely have other things on it but nothing to high voltage .
Pull the fuse and see what happens .
Honestly I have never heard of this .
Unless the mirrors lit or damaged somehow from to much heat damaging the coating on the back of the glass making it not a mirror any more .
This sounds like a factory defect

when you buy a new glass look for one with the heater pad on it. you can buy the heater pads new but its cheaper to get them with the glass.

You can replace the glass separately, but the heating element is in the head of the mirror.

Most heated mirrors on vehicles are made together. In other words, just replacing the mirror may or may not fix your problem. It would be more economical to purchase the entire assembly and replace it.

SECTION 501-09: Rear View Mirrors 2002 Explorer/Mountaineer Workshop Manual REMOVAL AND INSTALLATION Exterior Mirror Glass Removal
NOTE: Exterior mirror glass is serviceable only on vehicles built after July of 2001.

NOTE: Passenger side exterior mirror shown, driver side exterior mirror similar.
All mirrors

1. Position the glass in the full up position.

1. Locate the notch at the bottom of the exterior mirror glass.

1. Release the exterior mirror glass.
   1. Insert a long flat-bladed screwdriver in the notch.
   1. Push the screwdriver into the notch until the glass is released.

Heated mirrors

1. Position aside the exterior mirror glass.

1. Disconnect the electrical connectors.

All mirrors

1. Remove the exterior mirror glass (17K707) passenger side or (17T675) driver side.

Installation
Heated mirrors

1. Connect the electrical connectors.

All mirrors

1. Position the exterior mirror glass on the exterior mirror motor.

1. Place a hand against the back of the exterior mirror housing and a hand flat against the exterior mirror glass. Press the glass in place until fully seated.

Heated mirrors usually have a symbol on them -- a small diagram showing squigley heat lines.

If you don't see this, it's probably not heated. But when you take the mirror off, if it's heated it'll have wires connected to the back.

Yes, you can replace a heated mirror with non-heated -- just leave the wires tucked out of the way when you install the new mirror.

change whole unit ,heater element burnt out by sound of it,try removing plastic cover on inside of door behind the mirror and you should see the connections,but iam sure heater element is U/S

you can google an exploded view of your wiring harness that leads to the wring of your mirror. However this will probably not be a compatible way of doing it. The mirror is disigned differently.