Hi,
So I have a 2005 GMC Sierra 1500 pickup that is in great condition. Recently, I have noticed that in the mornings on my way to work the blower fan would not run on the highest setting. After a while of driving, the highest setting would then work. This happened for about two weeks. Now, the blower will not turn on at all on any setting. Thought it might a simple fuse, but that looks fine. Should I take it to the shop? Could it be the blower motor that needs to be replaced?
Sounds like a loose/dirty/corroded connection at the fan to me. Stick your head down under the glove box and look for the fan connector. On some vehicles there might be a trim panel to be removed.
Pull the connector and inspect - both the wiring harness & plug on the fan. Clean it up with some electronics cleaner & plug it all back in. See how that goes.
If you do that and get nothing, with the switch on thump the fan housing with a rubber mallet or block of wood or something. If that gets some life out of the fan then you probably just need to replace it.
After that, I don’t know if you need a shop but you need someone who knows how to use a multimeter to check for power. You’ll be left with a switch problem, some other wiring problem, or still possibly a bad fan motor.
I would check the resistor. Its in the heater box just to the left of the blower motor I think.
I checked the resistor and while doing so found that the wiring harness connection was melted and the resistor fried. Turns out, it is a GMC defect for certain models and years, and the dealer is going to replace free of charge!