A/c help

FlSD · Oct 1, 2014

Ok so I know their might be a thread on the a/c and maybe I haven't found it. But I am at a halt with my a/c. I've replaced the cycle and cut off switch, drained and refilled and checked the clutch gap. I'm don't know what else to do or try except take it to a shop. I can turn on the a/c by the control in the cab and nothing but someone has wired in a toggle switch to the compressor and if you flip it, it will work just won't cycle. Can anyone point me in the right direction.

superpsd · Oct 2, 2014

Sounds like someone directly wired to the toggle switch. Look up the wiring diagrams and follow them to the problem...

Dantheman · Oct 2, 2014

This is usually a low pressure sensor problem or a control switch. It was bypassed with a toggle switch to 12v+ which in turn also bypassed the high pressure sensor.

JLDickmon · Oct 4, 2014

man.. talk about a shade tree fix..
Yeah. I agree with Dan.
The previous owner had a control circuit problem, and cheaped it out by wiring the toggle switch in.
Seemed like a good idea, but you can ice up an evaporator in a heartbeat with no low pressure cut-out.

Zaairman · Oct 4, 2014

You said you drained and refilled the system... did you vacuum it down? Something is not telling the PC to kick the clutch on. What are your high and low side pressures at 1500 RPM?

FlSD · Oct 4, 2014

Zaairman said:
You said you drained and refilled the system... did you vacuum it down? Something is not telling the PC to kick the clutch on. What are your high and low side pressures at 1500 RPM?

My step dad hooked up the machine at his shop and that was in the middle of march so I cant remember what the readings r.

FlSD · Oct 4, 2014

I traced the hot wire on the toggle switch it leads up to the compressor and goes in to the cab under the dash

FlSD · Oct 4, 2014

The test light shows no power but a very dim ground (my geuss a short some where) and one of the other wires gets a perfect ground, but that doesn't explain why I'm not getting power to the switch on the evaporator. I went from the pig tail that comes off the harness on the firewall and plugs in into the harness for ac. My geuss I think the pcm could have bad pins or contacts for the ac since it is pcm controlled.

Arisley · Oct 4, 2014

What is a dim ground?

Ground is like pregnant, it either is or isn't.

FlSD · Oct 7, 2014

The test ligyt was very dim but I'm guessing their are two grounds and the other was perfect

Zaairman · Oct 8, 2014

It sounds to me like there are a few possible issues...
1. Bad switch on your HVAC controls (doubt it)
2. Low freon, so previous owner installed a jumper switch to get clutch to engage
3. Bad low pressure switch, so PCM won't kick on clutch, so p/o installed switch...
4. Bad PCM isn't sending voltage to the AC clutch.

The first step is to get your freon level up to spec.