My heated mirrors are not working on my Peterbilt 579.
The mirrors won’t defrost or clear up in cold or wet weather. I’ve checked the mirror heat switch and made sure it’s turned on, but the mirrors stay cold. No warning lights on the dash. Both mirrors are affected. Before I start tearing into the doors, what are the most common causes for mirror heaters not working on this truck?
Is it usually a fuse, relay, bad switch, wiring in the door hinge, or the mirror glass itself?
Any tips on where to check first would be appreciated.