Update....

Sensor is good. Robbed one off of my donor Blazer, checked it as per the video and installed it. Still no joy. Checked the old one and its good too. Jumpered the A/C relay ( gave it a ground signal, it picked up, clutch engaged and had nice cold air. At fast idle, had 30 psi on the low side and 110 on the high. That all checks good.

Pulled the plug(s) from the PCM, no continuity to the relay. What else is there in that circuit? A switch that stops the compressor when the throttle goes wide open maybe? Short of taking the harness apart and tracing that wire that provides the ground to the A/C relay......

Just had shoulder surgery 5 weeks ago and just not quit up to pulling the dash apart and seeing if there's anything going on there.

 

I've seen Sonoma wiring diagrams (not exactly matching Your sensor & wire colors) and there were two pressure switches on hi & low side. Maybe You've got another one? Too bad nobody has the diagram of Your installation.

 

Sounds like you have one of three problems:

No call for cooling from the dash selector to the pcm. That signal comes in on pin 36 of the PCM on a light blue wire. Probe that wire to see if the signal makes it to the PCM.

The compressor relay coil gets energized by grounding the low side via pin 55 on the PCM with a Dk Green/Wht wire. You can probe it at the pcm to see if it goes to gnd with call for cooling. You can also pull the connector and see if you have continuity to lug 1 of the relay socket.

There may be a wiring or connector issue. If thats all thats left then we can identify the connectors and wires to trace it down, or run a new wire if that easier.

George

 

Heres your diagram (I think).

Where is this switch located?

George

 

Thanks George!

Now got something to run with. I'll get on it tomorrow evening after work.

I'll post results.

 

Update.
Yes, get a call for air on terminal 36 12 VDC. No ground signal out of terminal 55. PCM internal relay is bad.

Now, do I run a wire to the relay and provide a ground via a toggle switch and enjoy cool air or do I look for another PCM.

A replacement PCM.... Will I need to program it or just plug it in and go?

Thanks for everyone's help on this.

 

You can do it with a toggle switch but then the system will not cycle and will not shut down if there is a fault condition.

You can attempt a repair or have a rebuilt PCM programmed as a clone of your original so its plug and play. There are a number of people who do this. One choice who gives a lifetime warranty and will try to repair first:

AES Modules | Rebuilt & Reman Control Modules

George

 

Well............

Here's what we did/checked..
Relay controlling the compressor is good
Pulled the charge, weighed it and put it back to ensure we have the correct charge. Compressor and charge are good.
Get a call for air from the dash panel.
Pressure sensor is good, performed test on it both on and off the vehicle, replaced it with a known good one.
Wiring between all components checks out good, no opens and no grounds.
Rebuilt PCM,
Still no A/C.

If I provide the ground to the A/C relay, I have 40 degree air blowing out of the dash vents.

Thoughts ideas? I'm about ready for the toggle switch fix, although I'd rather fix this right.

 

When was the PCM rebuilt?

George