Help with AC please.

[Dave5180]

I have a 95 RCSB, when i bought it, it didnt have the heat and ac controls. I ran without them for a while, but i just got my new controls in from rockauto.com. I pluged it in, all the lights come on, but nothing happens, no fan...nothing. I have checked the fuses inside the truck and under the hood. I really have no idea where to start troubleshooting to get this working. Any help will be greatly appreciated.

Thanks, Dave

 

[1low95GMC]

did you order the controller for a 1995 year truck? the 1995 ac controller was different from 96-98

 

[Dave5180]

Yes I made sure I ordered the correct one, and if i understand correctly the only difference is the wiring connections and this one plugged in

 

[1low95GMC]

The 96 plus controls will not work with a 95. Some one with more experience will chime in later, thats all the the info I got

 

[duanes7]

Not sure if you can see the actuators or anything under the dash. Looking at my manual, you might be able to switch the controls from heat to cold and see if the actuator for the heater core flap moves. I believe it's on the front of the heat/ac plenum just to the right of the heater core. I believe that actuator for the vent/floor/defrost is on the left end of the heat/ac plenum, middle of the truck. Might try to change the ac positition settings and see if that actuator is moving. If you see these moving then you know the failure is only in the blower and if nothing moves then it's a larger issue.

I know you checked the fuses, but figured I'd list them anyway: blower has A/C Maxi fuse 3 underhood and HTR-A/C fuse 12 inside, compressor has A/C Compressor Clutch relay, IGNE mini fuse and A/C Comp mini fuse underhood and HTR-A/C fuse 12 inside, air delivery and temp has HTR A/C fuse 12 inside.

I can't see any one thing that would keep the entire system from working except fuse 12.

 

[HIGH BOWTIE]

Maybe a bad blower motor.

 

[Dave5180]

Update...I pulled the blower out and tested it with 12v from the battery, spins like a champ. So I checked the power inside the truck with the selector on medium and it shows power. Come to find out the connector on the ground wire was not making contact, so I cut it off put a ring terminal on it and viola! my blower works. So I tested all the speed setting . It works on all except hi. Not really that big of a deal I can figure that out some other time. I started checking the linkage for the selector and found it was in a bind, got it right and now it will switch between all of them. Now the next order of business was the ac itself, it isn't doing anything at all, not even trying to engage the clutch. I have found all of the connectors for the compressor but I seem to be missing the one that connects to the drier/ accumulator. Does anyone know where that goes to? Sorry for the long post but I feel like I need to be thorough in order for you guys to be able to help. Thanks Dave

 

[duanes7]

Ah the ever forgotten ground. Good job.
When the blower switch is on hi, the power bypasses the resistor pack, and goes to energize the high blower relay and the power is run direct to the blower. It's ground is the same as the one for the air and temp motors so it's not that. It's power comes from the A/C maxi fuse which you've already tested. Sounds like the relay is not energizing.

Power for the compressor comes from the underhood A/C Comp mini fuse. You can try bypassing the underhood a/c compressor clutch relay to see if the compressor kicks on. I show a jumper between b4 and a6 should do it. With the jumper the low pressure, high pressure, and compressor cycling switches all should be out of the system. If you read 12v across a4 hi and b6 lo, then the control module is trying to turn on the compressor.

For some reason I think the a/c compressor relay and the fuel pump relay might be the same...

 

[Dave5180]

Well I thought I was making good progress on getting this situation resolved, but when I got in my truck earlier, the fan was no longer working. I grabbed the test light and now I am getting power back through the ground, so I guess I will spend the day tomorrow tracing wires and hope I find the problem. As for the bypass jumper you are talking about, where exactly would I be jumping them? Thanks for your help, Dave

 

[duanes7]

As you stand at the driver's fender with the fuse box in front of you there are three relays on the far (passenger's) side. The middle one is the AC relay. Pull it and jumper between the closest left terminal (should be constant 12v) and the farthest right terminal. The other 2 are the terminals to turn on the relay.