Thought I'd hook my A/C back up, had the belt off since the rebuild, temperatures around here up in the 90's. Put the belt on and turned on the A/C, got the light, but the compressor isn't engaging. Checked the line going to the compressor and no DC. Should be 12VDC? Light is on, so fuse has to be good, checked it anyways after searching for and finding the bugger behind the glovebox. From the schematics it goes into the A/C Amplifier, where is this located at, don't see it in the manual. Any other hints appreciated. Gonna try and jumper the compressor to see if it comes on. Gonna need it for the onboard compressor install I'll be doing shortly.

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AC Amp behind the glove box, black box that has an RPM knob. Also, low pressure switch:



http://www.4crawler.com/4x4/CheapTricks/22RE_Engine_Pix/20.html

Thanks Roger, you come through once again. Although, I think I'll wait to check it until tomorrow. Supposed to be cooler, I'm sweatin just sitting here typing this. <img src="/forums/images/graemlins/scared.gif" alt="" />

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Check the voltage at the low pressure switch (behind the grill, near the r/s headlight). If you have voltage there, put a gauge on the low pressure fitting at the compressor. Either the low pressure switch is bad, or you are low on refrigerant.

Most likely your system is low on freon. Since the compressor's oil is mixed into the system with the freon, the low pressure switch won't let the compressor come on if the system is low or empty. Running the compressor without oil will kill it quickly. So your system will need serviced/recharged.

It's also possible that the low-pressure switch is bad, and is saying you don't have enough refrigerant/oil in the system even though it's fully charged. The easiest way to diagnose this is to check the charge in the system. If it's low, you've found the problem (charge it). If it's not, you've still more than likely found the problem (pressure switch).

To check the clutch, on my Toy there's a connector in the clutches wires about 6 inches from the compressor. Most liekly this is where you found it's not getting power. You can hook it up straight to the battery for a second and listen for a loud CLICK. Which wire is + and which is - doesn't matter, the clutch is just an electromagnet, and I've never seen one that was polarity-sensitive.

yeap - check for continuity on the low pressure switch.

Was out driving around today and heard some belt squealing. Parked and popped the hood and saw the compressor clutch engaging and stopping/belt squealing, so my guess would be the compressor probably sat too long and is no longer any good. Never used the A/C or even tried it when I first got the truck and havn't inquired with my brother, the previous owner, if it ever worked.
Just went out and applied 12vdc to the compressor, seems to engage and disengage fine. No funny noises when spun by hand. I"m sure I had the belt tight enough, hmmm, maybe I better check the tensioner pulley, didn't do that. <img src="/forums/images/graemlins/rolleyes.gif" alt="" />

Make sure your pressure on the low side is 25-45 with ac on and blower running. Had same prob and it was just low on juice. (Prob I have now is not getting cold enuf. going to check evap drain tomorrow. Some of the other guys said drain may be plugged. )

Any time mine gets warm, I liberally spray off the condensor... It seems bugs don't like to cool off the truck much. They clog it up, and not enough air passes through the system.