95 Heat/AC issue

[jham0077]

I have a 95 Tahoe, 5.7 w/5spd. I've got a heat/ac problem. The only thing on the control panel that works is the ac button and the compressor clicks when you select a defrost mode. The fan, temp, rear defrost, and position selectors do not function. With the key on, engine off there are 12 volts on the blower ground. I can ground the blower either directly to the battery or even the door hinge and get it to blow in 3 speeds(no high). But nothing else will function though.

I found a diagram showing the blower motor sharing a ground with the 3 blend doors. When I disconnect them, I loose the 12 volts on the blower ground. I have checked continuity between the grounds and the right cylinder head ground. The meter beeps, even grounded back to the battery, it beeps.

I've Googled this issue and found quite a few instances of this problem, but never a fix. Any help is greatly appreciated. Thanks.

 

[SunlitComet]

what color is the wire you see voltage on WHEN IT IS DISCONNECTED FROM THE BLOWER MOTOR.?

 

[jham0077]

It's the black one that goes on the bolt on lug on the blower housing.

 

[SunlitComet]

same thing when motor modules are unplugged ? if not plug in one at a time and retest if one puts voltage on that ground it should have blown a fuse unless high resistance short in the door motor module.

 

[jham0077]

No voltage when blend motors are unplugged. I was gonna do the process of elemination by plugging them in one by one, but ran out of time today. I have not found a fuse blown... I wish it would.

Just 3 blend doors right?

 

[SunlitComet]

yes.

 

[jham0077]

May be Saturday before I get time to fool with it again. Its geting cooler here and its my daily driver, so somethinks gotta give. Thanks. I'll be back...

 

[jham0077]

Makes no difference which door motor I plug in, they all put voltage on the blower ground.

 

[jham0077]

Should I start peeling tape from harnesses and looking for welded wires?

 

[SunlitComet]

wait a second the ground wire of the motors put voltage on the ground? by any chance when testing on the meter are you putting pos lead on motor grounds and negative lead to a body ground?