A/C wiring diagram needed?

Hello,

Unfortunately, when relays are jumped out and left that way, nothing good comes of it. I'll post the diagrams for the system. A/C should work in Defrost mode too. There should be 12volts going to the High-pressure switch (which is located on the back of the compressor) when the Control Unit is turned on and there is an AC request. The High-pressure switch in this case will toggle the AC request on and off as needed. So, when you turn on the AC you should have 12volts on one of the wires at the High pressure switch, which will tell you if the control unit is working. I'll post the connector diagram too shortly.
The Low-pressure switch should have a Reference voltage at it too, it just happens to Ground on the same circuit as the compressor does. You can see in the OEM diagram that there is an internal resistor and voltage source inside the ECM. When pressure is low that switch will toggle on and off to signal the ECM. But as for diagnosing the control unit, just looking for the 12volts on one side of the High-pressure switch should come and go as you turn the AC off or on. As long as the system is not over pressurized it should start by the ECM grounding the control relay. If you don't get a voltage signal through the High-pressure switch when its first turned on there is either too much pressure or the switch is stuck. Grounding pin 85 is just forcing the compressor on regardless of pressures.
The High-pressure switch should be on the back of the compressor, I'm not 100% sure this is the correct connector, they have it labeled as the compressor clutch, except the wire coloring is for the high-pressure switch. The compressor clutch is Dark Green power feed and Black as Ground. Aftermarket diagrams are not always 100% correct. But I hope this helps. You may want to take a look at the connections on the underside of the fuse/relay panel, just to be sure there are no broken or burned-out wires where the relay sits.
You can check the ground also at the ECM on connector C2 pin 43, that's the relay control wire, Ill pull up the diagram for that if you want to check that the ECM is making ground for the relay or if the driver is burned out.

It looks like the ECM/PCM only has 2 connectors, C1 and C2, C1 looks blue and C2 should be green. Pin 43 is a dark green/white wire for compressor relay control.

https://www.2carpros.com/articles/car-air-conditioner-not-working-or-is-weak

If there weren't two different connectors on the old compressor, it might be built into the clutch circuit. But on the wiring diagrams it lists the compressor clutch as being a dark green wire with black being the Ground for it and the AC high pressure switch as a light green wire and a dark green/white wire going to the ECM, and both OEM and aftermarket diagrams are the same. With the High-pressure switch located on the back of the compressor. What colors wires do you have on your compressor and were there any other wires to the old one?
It's strange also that the OEM connector on the compressor is listed as the compressor clutch but the wiring is for the high pressure switch, so something is wrong here. I'm going to look for some more information. If you can tell me the 2 wire colors on the compressor, we'll see if we can sort this out. This service info is very misleading.
I know this is the 2500 series, but is this a cargo van, with manual ac? Even with that the ac compressor clutch is showing a dark green wire and a black wire for its ground.

This is what they are showing for the pressure switches. I haven't seen any other locations for it so far. I'll post whatever is found.

Ahh that's awesome, something just didn't look correct there. So glad you found it. Nice work. I'm glad to help and have a nice day.