AC no worky

I've tried every test I can think of. I recently fried my computer (1992 XJ) which was actually running a 93 computer.

I swapped in 94 computer and the AC no longer worked.

at the relay: I've tested the ign power in, the switched power in at the relay and jumped power to the clutch (which engaged it) I also ran a ground to the relay and the clutch worked but stayed engaged.


I've also tested the pressure swith and jumped the wire from pi 34 on the computer to the relay and still nothing.

I'm at a loss,...any thoughts where to look next?

check the pin on the ecu it may be bent or pushed in. or wired at a different spot.

Yeah I checked the wiring diag for the ecu and relay for 92 and 94 and they match. also checked the pin and it is straight and clean.

This may be irrelevant to an R12 system, but the only other input left is the fin-temperature sensing switch? Total shot in the dark, but that's what I recently left unplugged (on mym '96) and had same symptoms. Perhaps your computer is looking for the input which it doesn't(?) have - or maybe was jostled or left unplugged?

thanks, already tried jumping the switch

You tried jumping the Low Pressure Switch - did you test with a meter to see if it was receiving power?

Haden't thought about that, assume I probably can't get away with a test light?

Don't know why a light wouldn't work, but I don't know anything about electricity and I've never used a test light. Come to think of it, I don't know anything about the jeep either

However, if my manual is correct (or if I'm reading it correctly ),the power supply/signal to the low-pressure switch actually comes from the output of the fin-sensing switch rather than directly from the ECM.

Figured it was just a switch, but according to the parts catalog, there's a relay attached to it. Was thinking that even if you jumped the switch, the relay portion might be bad.

i only have a diagram for the 90. but it cant be something that complex if all you did is change the ecu. unless the a/c burnt up your ecu. but look at any a/c related stuff near the ecu. i have no idea where the ecu is but im assuming under the dash on the passengers side?