Hello, I have a 2006 gmc 1500 with automatic temp control. Four months or so ago I replaced the resistor. Everything worked good. Last week I had no air coming from my vents.

I checked the power to the resistor and the blower motor.
The 40 amp fuse is good.
I checked the blower motor all is good.

 

So the question is, does the blower spin? Spin slowly? If your blower gets power and ground, and the fan still doesn't spin, then your blower is bad.

 

The blower motor spins fast

 

So you're having a problem with the air coming from your dash vents? Will the system switch to the floor vents or defrost? If you can, use a tech2 or maybe even a snapon scanner might do it, see if you can get in and read the codes in the HVAC control module. I'd guess it's probably a mode control valve actuator if the modes don't switch. Just a guess though, it would be helpful to know if there's any codes stored in the HVAC module though.