My ram is a 1997 2500 with the 5.9 v-8. My A/C compressor will not engage. Over the winter i put a new motor in it, and in doing so i removed the a/c compressor. I know with no refrigerant in it, it will not engage. I have a good connection at a local repair shop, i took it up there yesterday and had them suck all air out of the system, leak check it, then i proceeded to fill it and the compressor would not turn on Since then, i have been trying to locate the problem. I hooked a test light up to the connector that goes directly to the compressor with both the a/c selected on and off, and got nothing both times, and i checked the ground on the test light when i did that. After that, i bypassed the evaporator by putting a paper clip in the plug (i read that on here) to make the system think it was full, and still no luck. Any help here would be greatly appreciated, I am going across state next weekend and a/c would be very nice. thanks for the help!

 

Looks like there are two fuses involved here.

Fuse 11 in Junction Block. (fuse box inside truck) Control circuit for A/C compressor relay.

Fuse J in Power Distribution Center. (under hood) Power feed for the compressor. Switched via relay in PDC, controlled by PCM.

So, either the relay isn't getting tripped, or, the relay isn't getting power, or.... the relay is just bad.

Pin 30 is the power feed TO the relay, for the compressor. See if you are getting power there. (Fed from fuse J)

85 and 86 are the in/out repsectively for the control circuit. 85 should have 12 volts, 86 should be ground with the A/C requested on. (controlled by PCM)

PCM monitors low/high pressure switches, to decide if to run the compressor. If either switch is open, compressor won't run.

 

i have no idea how this happened, but i was tracing wires under my dash, and the connection for the wires when you select the A/C is connected to nothing, and i can not find the female end of the plug under the dash. An idea where this is located would help a lot. Also all of these signs and symptoms make sense with that being the issue.

 

Looks like there are several connectors on the back of the HVAC controls, if it is in that neck of the woods, probably plugs into that.

 

there is a 20 amp fuse in the main fuse box for the horn, it was pooped so i replaced. The compressor worked for a little, then i shut it off. when i went to start it back up, the fuse pooped again, where is this grounded at?

 

The horn button provides ground. Probably right in the steering column somewhere. Probably have a short in the wiring somewhere.

Did it blow the fuse when you hit the horn? Or before you even touched it? The control circuit, and the horns, are both powered off that fuse. Horns shouldn't be getting power past the relay until you actually hit the button.

 

i never touched the horn, and if it helps, my horns have not worked for probably a year now.

 

Blown fuse would explain that. Must be a short in the control circuit somewhere..... Yank the relay, and probe terminals 85/86 for a short to ground. (no fuse in place please.)