Kolenc

I get 12 volts on red wir pin A and no voltage on any fan pins B D E and F. So is that the control module?

mountainmanjoe

did you move fan speed dial to every position when you were measuring those pins? Was the mode dial set to anything but off?
is there 12V on both sides of the HVAC fuse? (#10, 20A)

well if you read the topic I linked to , the problem ended up being the ignition switch

Kolenc

Power on one side of fuse with fuse removed and checked fuse with voltmeter for continuity. Yes we checked all positions of fan speed. If it’s the control module do I have to buy on with a rear defrost because it’s a cargo van and there is no windows.

mountainmanjoe

I asked if there's power on both sides (with the fuse installed.)
The fuse has exposed tabs on the top of it that you can probe with your meter.
continuity is not a reliable test. Or you can measure the resistance of the fuse if you remove it.

If the fuse is fine, then you need to move on down the line.
Remove the control head, and measure for power on pin E of the connector.
(you may need some thin probes or a piece of wire to reach)

For the next test the control head must be plugged in. So you'll need to back-probe the connector or use piercing needles
pins G & A (when any mode is selected)

Next probe these pins on connector X100 (Instrument panel harness to the engine harness, left rear of the engine compartment near the underhood fuse block and the horn)
pins 2,3, 6 & 8 (orange, lt-blue, tan, yellow), depending on the fan speed selected

X100 is #3 in the drawing



you should replace with the same thing you have

Kolenc

Sorry but what is the control head? Thanks for your patience

mountainmanjoe

the panel on your dashboard with all the dials which controls the system.
GM's technical name for it is "HVAC Control Assembly"

Kolenc

Ok I checked power on both sides of fuses. Opened dash to get to control module. Pin E ignition has power. Went to plug it back in and now everything works again. Must be a bad connection on module or a wire behind it. Not sure it all works for now. Thanks for all your help

If it was the module which I can’t find because no one has it can another one for this vehicle work even tough I don’t have heated mirrors as an example?