I hate to pull you to another forum than this one but I normally bounce between these two... I'm currently having my own A/C battle so I share your pain. From what you are saying, maybe try what they suggest in here and jump 12v's to try and get the coil to pull? Maybe that's the culprit.

A/C Compressor Clutch won't engage, tried the paperclip trick - Diesel Place : Chevrolet and GMC Diesel Truck Forums

Hope this helps, good luck!

 

This may sound stupid, but your a/c system is charged correct?

 

I would start by inspecting the system components for any signs of leaking. If non are found perform a leak test and charge with a calibrated A/C machine. Then begin to check switches and wiring.

 

Does anyone know of any wiring diagrams for this ac system on our trucks? I can jump the compressor and get the coil to engage as far as charged it shouldn't matter if I jump the low pressure switch, unless by some miracle it has to much pressure.
Anyone know how to jump the high pressure switch just to see if I can get it to do something, I have no clue where to even start chasing things down.
I'm just starting to get annoyed with 90 degree days and no ac

 

Check the A/C charge before you do anything. I'm betting you are low on refrigerant.

 

But doesn't the paper clip trick bypass the fact it would be low of refrigerant?

 

Manually engaging the compressor like that can cause damage. The compressor relies on the oil in the refrigerant for lubrication. Check the charge in the system before anything else.

 

I'm having the same issues. Will the compressor not engage if the refrigerant is low? Is this a self protective feature?

 

Yes you are correct. Low refrigerant will cause the system to shut down and protect itself. Get you system charged checked first!

 

Mine does this after I wash under the hood. Evidently water gets in a connection or something and the A/C quits completely. The first time it did it I went thru all of the old tricks to make it work and nothing helped. Low and behold, as soon as it dried out under the hood everything went back to working. I need to get under there and figure out what is causing it but I guess until it starts to happen more often or wont right itself I will just not worry about it. P.S. I never does it when it is raining, only when I wash under the hood.

 

Ok, I will get a can of refrigerant today and recharge the system in hopes of getting mine to kick in. Thanks.

 

DIMEBAGSDECIPLE -

I would stop washing under the hood of your truck ASAP I cannot tell you had bad this is for your truck. Yes the connections are water resistant but at all costs avoid getting water in the engine bay. I have seen so many failures with people who detail their engine bay or rise them down. The only time I ever put water to the engine is to rinse after a repair and am very careful of connections.

BRICH60 -

I would not just do a can with the RED,YELLOW,GREEN gauge because that is not accurate. I would suggest going to a certified mechanic and paying their menu price for A/c evacuation and recharge. I would also inquire about adding dye to the system. They should not charge you any extra labor just the cost of the part. While they are doing the service you can ask them to hold it in a vacuum for at least 10 minutes to see if it holds. This is park of a leak test. Most places will charge 80-150 for their service. This ensures that you get the proper amount of refrigerant in the system and does not over charge it.

 

DIMEBAGSDECIPLE -

I would stop washing under the hood of your truck ASAP I cannot tell you had bad this is for your truck. Yes the connections are water resistant but at all costs avoid getting water in the engine bay. I have seen so many failures with people who detail their engine bay or rise them down. The only time I ever put water to the engine is to rinse after a repair and am very careful of connections.


I don't really "wash" under the hood as in detail it. I just spray it down when it gets too dusty or muddy under there. I have learned to just focus on the firewall and fender skirts and shroud, ect. I think the problem I have is that the A/C was getting wet and in turn making the whole thing not work regardless of how I would try to override it. The guy who started this post should check out his A/C relay. If it is bad it will cause a total A/C shutdown.

 

I always wash my engine off because its always covered in mud so its getting wet regardless

 

Well had a mechanic check my systems charge it was good so he pumped it out and changed the low pressure switch pumped it back up. And the switch change did not help the problem. Any suggestions of where to go now? I really think something isn't sending the signal to turn the ac system on. I think it's the heater controls in the cab but I'm not for sure and they are like $200 so I want to make sure that's what it is before I buy them.

 

There are 2 videos by Richpin06a that give you very good, clear, concise instructions about troubleshooting your a/c system.

This is the 1st of 2 videos: https://www.youtube.com/watch?v=PMM80xlon3U

If you have a digital tester, spend some time gong thru all the steps in the same manner as Richpin06a. You may or may not find your answer there.

 

Ok this is what I found. The low pressure switch is fine. Not sure how to test the high pressure switch. Testing the ac compressor relay I have power to the #30 spot, power in the #86, no power at the #85 spot. And the #87 spot test good for continuity over to the compressor. Checked the ign3 fuse under the dash and it checks out ok. So does it sound like there is a problem with a wire going from the under dash fuse box to the fuse box under the hood?

 

Has anyone ever had this problem? I'm starting to think it's the controls in the cab but I'm not sure how to test them and see if they are bad. Has anyone heard of them going bad?

 

Check the ac fuse inside and there should be a compressor fuse as well. Also switch out the relay with a known good one to be sure. Sounds like it could be a relay problem. If it were me I would change out all the ac related fuses with new ones and the relay as well. Just to be sure.

 

Already did that. I started test the spots where the relay plugs in. I have power in two of the three spots that should have power and the fuse under the dash is good. It's something with the wiring on the solenoid side of the relay.

 

Andrew

Did you look at the You tube videos that were posted by me? Very concise, step by step troubleshooting for your a/c system. If you went thru those steps, I don't think you would have questions about where the problem is. Possible of course, but the buy is very thorough.

 

Yeah I watched them and that is where I figured out I have a problem with the socket that the relay plugs into. What I am trying to figure out is what sends power to the number 85 spot when the truck is running. Does anyone know of anywhere I can get actual wiring diagrams for the ac system?

 

Here you go. Look for your year: GM UPFITTER - Body Builder Manuals

 

Terminal #85 is the ecm control (ground). Do not use a test light to check for ground there. Either try swapping relays with the horn (or other similar relay) or take it to someone with a scanner to find out why the ecm doesn't want the a/c engaged. If you're careful you can jumper 30 to 87 and make sure the clutch is capable of working.

 

That's what I needed to know

 

Thanks guys

 

What is terminal 86 then? I have tried swapping relays and that didn't work