Two problems related to dash wiring have been reported for the 2005 GMC Sierra. The most recently reported issues are listed below.
Heater /ac fan 5 speed not working and wires to blower under pass side hot to the touch and plastic jacket on wires burning off also connector with same leads to blower melting to socket unable to unplug ( unable to use heat or fan without build of heat on wire) lots of burning smell.
The blower motor would work and then not work and when it worked for a long period of time, smoke would come out from under the passenger dashboard. I removed the cardboard cover and saw smoke from the connection to the blower loter and the connection was hot to the touch so I pulled it off from the blower.