Air won't blow on 95' Jimmy
 

Hey everyone, I seem to have a problem with my ac/heat. I had a problem for a while where the air would only blow when it wanted... usually after a few minutes of driving it would kick on or after fast acceleration, and then more recently it always worked. A few days ago it stopped working completely... so i started replacing parts. I have checked the fuse, relay and electrical connections (just to make sure that they are tight and in place), I also replaced the blower motor and the blower motor resistor. Is it possible that the blend door actuator could prevent any air from blowing, and preventing the blower motor from turning on? Is it common or more likely to have vacuum or electrical issues? When I change the temperature setting I can hear something like an actuator moving, but I don't hear anything changing when I change it between defrost to vents.
Any ideas?

Vacuum connections are all good, all 3 actuators are functioning, it has a new motor and resistor. Voltage reads at 12.84 at the motor, but it won't turn on. Is there a control wire? I know the purple from the relay feeds to the motor, but the relay checked out ok too. What else could cause this problem?

This morning it kicked on after going over a little bump, stopped again, and then turned back on. It has stayed on, so I won't complain... but I'm just hoping it lasts!

Sounds like a faulty/broken wire somewhere if it kicked on after a bump. Most likely will go out again unless you trace the wiring for the faulty wire and replace it. Just FYI, wiring sucks... Maybe start at the blower motor connector since that would be the most exposed/easiest access to any of that components wiring.

Found the problem
 

I followed some wiring and found a bad connection on the black wire from the blower motor. It goes to a 4 plug connector and was burned up there. I think I willl have to run a new ground for the blower.

I ran a new ground and the blower is working great now with no problems. I should have checked the wiring first, it would have saved me a lot of time!