Archived compressor clutch relay ground?

[BDaugherty]

Truck is '97 Ram 1500 Sport 2wd 5. 9 gas auto.

A/C compressor clutch coil was shorted. Had . 4 ohms resistance. I ordered a new one off Ebay. The problem now is that I don't have a ground at the compressor clutch relay. I have power, but no ground. There is ground at the clutch from the high and low pressure switches, but not at the relay? Where does the ground signal come from? Is it the PCM? If so, is there a good way to wire around it?

 

[Sticks]

I presume you are talking about the relay in the PDC?

The clutch itself according to my diagram is grounded at the clutch. If you have a 2 wire plug from the clutch, trace the wire and see where the ground terminates.

The relay coil are pins A2 (Ignition + ) and C1 at the PCM.

The AC select and request (dash switch and High/low pressure sensors) are C22 and C23. The sensors are in series and parallel to the switch, and the dash switch closes the ground. PCM is sensing load draw from any of the three to close the AC clutch relay I am guessing.

 

[Missouri Mule]

From 96 Factory Service Manual

AC operation

2nd paragraph

"After receiving the A/C request signal,the PCM supplies ground to the coil side of the AC clutch relay on circuit 13(dark blue/orange wire). Circuit 13 connects to cavity C1 of the PCM.



Paragraph 4

The AC compressor clutch has a built in diode.

 

[Sticks]

Nothing like early morning pre coffee diagnostics.

 

[Missouri Mule]

The clutch grounds at G119 (black/white wire) front driver's side head. This ground is used for alot components including the PCM.

 

[Missouri Mule]

Sticks are you up late or did you get up early. No coffee for me it makes me too jittery.

 

[Sticks]

0300 wake up, every day whether I like it or not.

 

[BDaugherty]

Thanks for all the replies. It seems that I made things a little harder than they needed to be. After installing a new fuse and clutch coil, I tested the circuit with the engine off and key on before hooking it all up. It would appear that the PCM needed either a load or a running engine before it would ground the clutch relay. I was about to walk away from it for a few minutes when I decided just to hook everything up and see what happened. Well, what happened was everything worked perfectly. So now my dad's 1997 factory original A/C with 145K is working again. All it needed was a new coil, a single shim removed from the clutch, and a bozo son to get out of the way and let the factory system work work as intended... whatever the specifics of that might be.