2000 9400i mirror heat?

I think there was no switch back then, constant ignition power only. See if there is a fuse for it behind the glove box. The oldest diagram I have access to right now is for a 2002, it did have a switch. But something rings a bell in my head there was no switch for a few years around that time.

 

I checked at work today. All the diagrams around 1999-2000 did show switches. It is possible too that the truck was never ordered with heated mirrors, but the actual mirrors and door harness do accommodate it. Hard to say what a truck goes through over the years. Anyone could have added it too. Have you had this truck since new? If you give my the last 8 of the VIN, I can see how it was built.

 

I need the last 8, 6 won't do. If you have a 2000 I am guessing it should be YC053560? Does your truck have a N-14 engine? If so, your truck was built with heated mirrors. When I look at the general wire diagrams it shows a switch, but when I bring up the trouble shooting it shows constant power. I think it depends on the style of mirror. Corrosion likes to build up in the door path through connectors and wiring likes to break where it passes trough the door.