Only thing I can come up with is the wires going up into the fuse block where the rear defrost relay (RR DEFOG label in the manual) are switched so when the relay is activated, which normally turns on both mirror heaters and the rear defog, is turning off the mirrors and turning on the rear defog.
You need to unbolt the fuse block mount so you can lift it up and pull the RR Defog relay wires out the bottom and reverse the two circuit wires but not the two supply wires. Wish I could say right now what colors they are, but I don't have that. Odd situation...
I have a 1996 406 GLX. Although both mirrors have heated symbols printed on them there is no switch as such like you would have for the rear window. This may be an addition on the Rapier and Executive models. The mirrors do defrost when the front screen heater is in use as hot air is diverted through the side of the dash. 2001 diesel estate HDI works when you switch rear screen heater on and after 10 mins both switch off
Not sure of the actual intent but in the S10 Blazers the power heated mirrors are turned on with the same switch that turns on the rear window defogger
The 2001 GMC Yukon has 16 valves.
The 2001 GMC Yukon has a V8 engine.
Hall of Mirrors - 2001 was released on: USA: 31 January 2001
The 2001 GMC Yukon is a gas-powered vehicle.
The 2001 GMC Yukon has a 4-speed automatic.
The 2001 GMC Yukon has overhead valves (OHV).
False Mirrors was created in 2001.
The 2001 GMC Yukon is 16 ft. 6.8 in. (198.8 in.) long.
The height of the 2001 GMC Yukon is 6 ft. 4.7 in. (76.7 in.).
The 2001 GMC Yukon-XL has 16 valves.