Howdy,
Recently picked up this rig and absolutely love it for what I need. Everything works splendidly, especially considering its age and miles (250k+).

Figured I'd go after some of the 'low-hanging fruit' so I've fixed the rear lift gate supports, little lights, things like that. Working on the A/C now and this is what I've run into:

System is recently converted and has a partial charge of r-134a.

Compressor is not engaging and I don't want to put any more refrigerant in the "collector" until the thing cycles. I've tried putting a jumper across the connector that was on the low-pressure switch, no change.

I've also checked the fuse and cleaned the electrical connector that actually connects to the compressor. I don't know if voltage is supposed to be there, so I haven't checked that yet for fear of shorting something. If I get time, I'll spend some time with the schematics (if they're in the Chilton manual I've got), but it's been a while since I've done all this so thought someone might know other places to check.

I saw in another thread that the relay was the one on the inside of the driver's side fender, closes to the firewall, but I think that's a fuel thing. Wasn't sure, so I have a couple extra of those relays. (Haven't tried swapping them out blindly),

Not sure what else you might need to know, so let me know if there are blanks to be filled in and I'll go look.

Thanks for the help!
-R

 

Ok, so...quick update for those keeping score:

I looked at the wiring diagram and saw that on the connector to the compressor, there is a green wire (12v+) and a black (ground/common). There is also a diode (no idea why...any thoughts?) but right now I just want to cycle to compressor so bypassing all that.

Put 12V directly the compressor and it engaged. Noisily, but it engaged. My guess is that it hasn't cycled in many, many years so will take some time before the oil has worked its way through the system. By the time the first can of r-134a was in the collector, the squeaking stopped but there was still a fairly heavy load on the engine and by the end, the surface of the compressor was wicked hot.

Still not certain why it won't engage on its own. One idea I have is a bad ground. On the connector to the compressor, I measured 122k Ohms between the ground wire and the negative battery terminal. So I'll start there and see where that takes me.

I'll keep you posted.

 

Cars are more cooperative on Sunday mornings.

It was a bad ground. I flipped the leads on the multi-meter when measuring from the connector ground (compressor) to the negative battery terminal. Measuring one way, got about 122k Ohms, flip the leads and get an open circuit.

I remember the diode on the connector and realize that the resistance I'm measuring is through the positive end of the connector (Didn't isolate the ground wire). Ran a jumper from the battery to the connector and turned everything on.

The compressor would kick on, then shut off, then kick on, then shut off...and so on.

Then I remembered that the system only had a partial fill, so whenever the compressor kicked on, the system pressure would bottom out, probably opening the low pressure switch on the collector.

Pulled the connector off of that, ran a jumper across that, then Max AC and compressor was on for good now.

The ground wire from the compressor disappears into a wire loom and joins up with a bunch of others. I think my best bet will be to just run a new wire to the ground on the firewall.

The compressor was back to being crazy noisy when it came on. Any ideas what needs to be done there?

(Posting all this in case someone has a similar issue sometime in the distant future when Skynet is controlling all the machines and the only way to win is to disable their cooling systems).

 

Not much you can do about a noisy compressor. If it is not leaking and blowing cold I would not worry too much about it. Was there any Freon in it before you added Freon? If the system was empty, you really need to pull a vacuum before adding Freon.