1994 Laramie 4x4 5.9L

I am stumped. A/C quit working a couple weeks back. A/C compressor will not engage. Can find no mechanical problems. Freon is charged.

Only other symptom is that when I turn on the A/C switch in the cab, it blowsthe Horn fuze in the fuze box underhood. ???

I can find no wiring diagrams, even ones topurchase, to further troubleshoot electrical. All other electrical works.

I hope it's not acompressor failure.

I tried searching the forms for the last couple days, with no luck, so I'm risking a new thread.

 

Sounds like the ground for the A/C relay has a direct short to your horn power wire somewhere. Does the horn work before the fuse blows? Have you done any tinkering around back by the firewall in the engine compartment or up above the steering wheel in the cab? Look for a pinched wire harness between those 2 areas. And if I'm not mistaken, the A/C relay is on that big fuse box too, so maybe some water got in there. Sorry, I don't have any schematics to look at to help further.

 

You can pull the A/C relay out of the PDB, turn on the air and see if the horn fuse blows. That will tell you which direction to look. If it blows the short is in front of the relay, if it does not, then it is behind the relay.

 

Thanks guys. I'll try your suggestions and see what happens. Without a schematic, I'm assuming the relays are the 1" square black devices that plug into the PDB.

Yes, the horn works fine before I turn on the A/C.

No, I haven't rewired anything myself. But that doesn't mean previous owners haven't mucked something up. I don't see anything from the engine side of the firewall, but I'll have to take a more detailed look up under the dash.

 

Here ya go, they have all sorts of wiring diagrams for ya. Should make things easier.

https://dodgeforum.com/m_873481/tm.htm