It's -28 C here today. I fired up the truck this morning and after a 15 minute warmup, I head out to fuel up and do some shopping. After a few minutes of driving the heater fan motor shuts down and almost immediately starts agains then shuts down and smoke starts coming out under the passenger side dash in the area of the heater. I shut the heater off and continue on to fuel up - sans heater. The heater was set to defrost and the blower was on high at the time of failure. The fan won't work on any setting now. So, is the heater fan motor fried or something else? There was no noise. no squealing, nothing before the failure. Is this a diy project?

Check the blower motor resistor and the conenctor for burnt terminals.

Is the resistor located close to the blower motor?

http://www.dieselplace.com/forum/showthread.php?t=277135&highlight=blower+resistor

Thanks a bunch for the info. Hopefully its the resistor and not the motor. Is the resistor only available from OEM?

I had this same problem last winter and it was the Blower motor control module, which was about $110 from the dealer. I had to take the plastic cover off the HVAC unit under the passenger dash and then remove two scews that held the module into place. I'm not 100% sure thats your issue, since it can be any number of electrical problems with these trucks, but I did a lot reading on here when this happened to me and that solved my issues.

Thanks to all who responded. I went to a GM dealer here to pick up parts but didn't know to specify manual or automatic HVAC option, so the dealer gave me wire harness/plug and resistor box for manual heater setup. Didn't have time to do it myself so dropped off at trusted job shop. They got correct parts for the automatic HVAC which is a small plastic 3 prong female connector with 3 short wires and the resistor box with the corresponding male plug. Stupid expensive for the parts but I was able to return the unused wrong parts. Fan runs fine again. Total cost was $384 with labor being $127 of that.

BTW, to all of you, save your receipts. A couple more trucks burn to the ground and there WILL be a full blown Recall.