94 C1500 Suburban HVAC Control Issue

[Kamd90Chevy]

Hey guys and gals, i bought my dad a 94 Burb a couple months ago and have been working on it off and on as my work schedule allowed. I got all the mechanical taken care of, some tires and brakes, new light kit etc etc. However, the one thing ive not been able to get to work is the damn HVAC controls on the dash under the original radio. The radio has long since been unplugged for an aftermarket unit etc. I've searched back to my 90 RCSB multiple times to compare connections with and without power at the connector, matched the HVAC wiring harnesses and colors, to no avail. Can anyone help here? My dad is on the tail end of healing from back surgery and this will be his daily for work in a matter of completion of physical therapy. Please feel free to ask questions and provide whatever help you can provide.

Thanks greatly in Advance,

Daniel

 

[df2x4]

So everything is hooked up properly and nothing works? If so, I'd guess that the control panel is faulty. You can get new ones on Amazon for $150 or so IIRC.

 

[Kamd90Chevy]

So out of curiosity I went to the junkyard and bought 2 other HVAC controls for about 15 bucks. i tried installing both of them and got the same results. So I guess i'll be ordering a new one. I want to take mine off my truck that i know works and plug it into his but i'm super sketch about if something is wrong i don't want to short mine out too. The battles we face with these old trucks lol.

 

[df2x4]

Well if you tried swapping two junk yard panels and neither worked, I'd guess your problem might be something else. I've heard of them going bad, but I can't imagine having the type of luck to pull two that already failed... Makes me think something isn't getting power. All your fuses good?

 

[Kamd90Chevy]

Well i had the 2 junkyard units with me at the house and i tore my 90 apart and hooked them up knowing mine worked, and neither used part functioned. So that ruled that out. And unfortunately that is my luck these days. Trying to avoid the $100 on the new one from LMC Truck. But i haven't made it back to the Burb yet to hook mine up to his and see if it works there. I've been hunting vigorously for a wiring diagram to try and do some diagnosis beyond what i could see. Even though when i used the test light the pins were all lighting up the same on my 90 as his 94. Beginning to wonder about the unit that controls it. But there again, i haven't ever had to go beyond the controls. I know the original radio unit control module in by the accelerator pedal, does that also control that HVAC power? Or is that in another location? I followed the wire as far as i could see through the main AC vent panel that pulls out to remove and the harness seems to run behind the glove box to the top of the heater box assembly.

 

[Kamd90Chevy]

Ok so i found out if u cross the 2nd pin from the left on the connector and use a test light to close the connection on my 90, it kicks the blower. So after everything else i tried it on the 94 Burb and it would only kick the relay (which i ended up following the wires to a bracket with 4 relays on) so when i felt the blower motor it was hot enough to burn you. So we took it apart and hooked 2 pieces of wire from the battery to the blower motor out of the truck, it spun backwards. Which the production date on the motor is 08/14/1994, so something has gone bad. Eating dinner now and gonna go grab a new blower motor assembly and a new relay. Guess we will see how it goes.