Heat/AC Speed Control Switch not working

[mnlevans]

Just wondering if anyone has had this problem with thier truck. The heat ac works but does not blow air. The blower fan does work. Sometimes the switch works and sometimes it does not. It is a 2005 GMC 2500 2wd truck. Trying to find a fix so I won't have to take in the dealership.

[sechracer]

Originally Posted by mnlevans

Just wondering if anyone has had this problem with thier truck. The heat ac works but does not blow air. The blower fan does work. Sometimes the switch works and sometimes it does not. It is a 2005 GMC 2500 2wd truck. Trying to find a fix so I won't have to take in the dealership.

You can just get a new switch, they shouldnt be that hard to put in. Just need to pop the bezel off the dash.

[hankthetank21]

pull the knob off and look at the backside of it..look to see if its rounded off or broken...it could just be that the knob isnt turning the post....happened to me.............

[jakeamondo]

check the blower motor first. remove the cover, passenger side under dash. disconnect the electric connection. run a fused 12v wire to the high speed terminal on the blower and a chassis ground wire to the ground terminal. you can also test the resistor terminals that control the speed using an ohm meter between the blower feed terminal and each of the speed terminals. there should be continuity and differing resistance at each speed termial. the terminals should be labeled GFEDCBA. G should be where the purple pigtail wire connects, F is the high speed terminal E is the groung terminal and the others are the various speeds. G, the purple wire, is the positive 12v feed.