2011 4500 AC Not Working- HELP!

[Gfunk720]

Hey everyone. I have a 2011 4500 that has had AC issues from almost day 1(13k Miles). It has been at the dealership at least 5 times and while they seem to band-aid the problem(for thousands of dollars) it doesn't seem to have ever completely corrected it. They have replaced the AC clutch, evaporator pressure sensor, and more. Needless to say, I'm a little hesitant to send it back over there and lose it for a while with little confidence that it will get fixed.

It had worked pretty consistently over the last 2 years though, and only in the last few months started working intermittently. It would work fine for a few days or hours, shut off when hitting bumps in the road, and work intermittently at start up. A few weeks ago it stopped working completely, and I can't seem to figure out why. I'm a little hesitant to start changing parts without knowing what exactly the issue might be.

1. Tested Freon levels with a real gauge setup- System is full and when it was working working blowing cold
2. I tested power at the relay, and found no power coming into the relay to go out to the compressor
3. The compressor seems ok, as if I jump power over at the relay it comes on.
4. One of the switch points on the fan speed selector already doesn't work, so I'm wondering if perhaps the A/C button on the HVAC control unit failed.

Does anyone have access to a wiring diagram for the HVAC system? I can't seem to find anything online, and even our chassis builder said he did not have access to it. I'd like to test to see if power/signal is getting coming off the HVAC control, but there are a number of wires off the control and I don't know what is what.

Has anyone else had the HVAC control unit stop working? Seems like that would be the culprit as it is the first thing upstream of the relay, but it could also be a wiring break or something. Just seems unlikely that a wire is damaged.

 

[NJMOPAR]

Shutting off when hitting bumps sounds like a bad connection near the suspension where it's most affected. Check the connector at the compressor.

You say they replaced the clutch, why not the whole compressor? I got a new (not reman) UAC complete compressor for $215 on Amazon last month.

 

[Gfunk720]

The clutch was replaced probably a hundred thousand miles ago now. Seemed like they were just throwing parts at it as they didn't know what the actual issue was.

If I don't have power at the relay near the upper strut mount, there is no way I'm going to have power at the connector the compressor. What ever is going on is upstream of the compressor, which unless I take the whole dash apart it is hard to know where it goes from there. I first want to confirm I have power coming out of the HVAC switches, which would narrow it down to a wiring connection between the switches and relay. If I have power coming in, but no power coming off the switches(the AC button does light up), then I know the switch panel may be the culprit. That said I'm not exactly sure which wires are which into the panel.

 

[NJMOPAR]

Sounds like a faulty switch if the relay isn't getting power. If you have power going into the switch but not out to the relay that would be my guess.

 

[Gfunk720]

Sounds like a faulty switch if the relay isn't getting power. If you have power going into the switch but not out to the relay that would be my guess.

Sort of what I was thinking as well. The switch panel is about $200 though, and many places won't let you return electrical stuff once used.

There is a lot of wiring that runs in through the firewall there so I was trying to see if I could get a wiring diagram to see if it went anywhere else before the relay, or if there were any designations for wiring colors that would allow me to test output on the switch.

 

[Livinalittle]

Do you live on a farm by any chance?

 

[Gfunk720]

Do you live on a farm by any chance?

No. The truck is actually a service body for work. The last few weeks of warm weather haven't been pleasant.

 

[Livinalittle]

No. The truck is actually a service body for work. The last few weeks of warm weather haven't been pleasant.

I only ask because I have pulled some pretty nasty mouse nests out of heater boxes before. They tend to cause all kinds of problems and are really hard to diagnose until you pull the thing out.