1990 GMC Jimmy full size A/C electrical problem
 

i have a 90 GMC JImmy 1500 that keeps blowing the fuse when i slide the selector to any A/C setting. I have disconnected all the components under the hood and one by one reconected them to try troublshooting. I think its the sensor that is on the condensor, b/c that the one that causes it to blow every time.. any ideas? i need this thing fixed fast.. acc62001@yahoo.com 6789975150

The HTR A/C fuse (25A) powers the compressor clutch (via the cycling switch) and also has a wire that runs back to the ECU (under the passenger side dash). Disconnecting the cycling switch will take both of these items out of the loop. It also powers the blower motor via the selector switch which further powers the high speed relay (if on high speed) or the resistor pack for the slower speeds. As if that's not enough, this fuse also powers the DRAC module (digital ratio actuator controller) for the speedometer as well as the RWAL (rear wheel anti-lock) module.

BTW, you might not want to post your email address & phone number on the open forums. You can get a lot of spam that way.

thanks for the heads up. ill keep all that in mind..The fuse blows even when im just sitting in Park. The thing also works fine on vent in every fan speed, so i dont think any of those are it. Maybe a short to ground?

It's gotta be something in the A/C request wiring between the controls inside and the cycling switch under the hood.

is the cycling switch on the compressor or is it the one on the condensor? sorry for all the questions.

Not sure... It should have a light green and a dark green wire to the connector.

Well, the verdict is in and that wasnt it..lol.. back to troubleshooting.. any idea if the green wires should be grounds? I used a test light and they are acting as aground, as i use the + terminal from the battery? Sorry. i dont have a multimeter.

The light green wire goes to the hvac control panel and connects with the fused power circuit when in MAX, NORM, BI-LEVEL, & DEFROST. The dark green wire goes to the compressor clutch and would act like a ground through the compressor clutch coil.

well, Im back. i am about ready to take it to a shop, if i cant figure it out soon. I replaced the wires between the cycling switch and the a/c control switch on the panel. Still blows the fuse..What about the possibilities of the system being over or under serviced? I have not done any servicing, but it has recieved the R34 conversion b4 i bought it..

Being low on refrigerant would not cause the fuse to blow. Have you checked the wiring between the fuse and the hvac controls?