Hello, after troubleshooting why my 2001 1500 would only blow hot air, it came down to a broken blend door actuator assy..
There are three wires. blk/lg is ground, blue/blk is power 14v, and the yellow/red is the variable voltage coming from the temperature control ****. You can put a meter on the yellow/black and the blue/black wires and it will go from 0 volts to 14 volts as you turn the
temperature control ****.

Hope this helps someone testing one.

 

good info. Did you have to remove the whole HVAC unit or can you do it without removing the dash?

 

Good post man, thanks for the information

 

You can check and remove it without taking anything else off. It's below the HVAC box, a bit to the left in the passenger side mounted below. Once you take it off you can move the door by hand to see if it's jamming. Fortunately mine is free...so far!