AC Question

[yogi_123rd]

I have a 94 PA that the AC don't work very good. Blows cool air, not cold air. The compressor will comes on, and immediately turns off. This occurs every 5 seconds. The freon level is at the max. I would suspect the compressor would come on and stay on for an extended period. It doesn't which I believe is the AC problem.

What controls the shutting off of the compressor. Is it a relay or is it that the control unit in the blower box?

[HotZ28]

Just wondering, how did you determine "the Freon level is at max"?
The older compressors such as yours, (HR6) uses the low side pressure switch to cycle the compressor off/on. On an R-134a system, the switch will make at around 40-45 psig to turn the compressor on, (clutch engage) and open at 22-26 psig to disengage the clutch.

[yogi_123rd]

I've looked for the low pressure switch you mention. I don't seem to have one. (My older lesabre has one though - I found it).

Where is it located on the 94 PA?

I think I have the new compressor type not the old one you mention.

I tried putting freon in, but it won't take it. I did fill it with freon a year before this so I assume there's plenty of freon in the system.

I still think the temperature controller may be the problem.

[HotZ28]

The newer compressors (V5) do not cycle off/on, they run all the time, if the controller is set on AC. You said yours is cycling, so it is the HR6. They did not start using the V5 compressor until 96-97. The cycle switch is on the side of the accumulator/drier. You cannot see it without removing the rain shield above the relay/fuse panel.

You need to have the system tested with a set of gages to determine high & low side pressure. You could very well be low on refrigerant and the system has a restriction somewhere, thereby causing it to refuse a charge due to high pressure on the low side. If the low side pressure is higher, or equal to the can pressure, it is impossible to charge anymore. That is why we sometimes recommend soaking the can in warm water to increase the pressure. Do not try to put anymore in until you know what the system pressures are. (High & low)

[yogi_123rd]

Problem resolved.
Apparently when there's low freon in the system, the compressor won't run to suck in new freon. Gee - great system.

I found the low pressure switch (under a cover next to the firewall) and jumped it to get the compressor to run. A little freon later, an the AC is blasting cold air.

[HotZ28]

Originally Posted by yogi_123rd

Problem resolved.
Apparently when there's low freon in the system, the compressor won't run to suck in new freon. Gee - great system.

I found the low pressure switch (under a cover next to the firewall) and jumped it to get the compressor to run. A little freon later, an the AC is blasting cold air.

Glad to here you found the pressure/cycle switch. You are absolutely right, the compressor has to be running in order to take Freon, and if it is low, it will not run unless you jump the switch. Great design!

Sometimes, even if you do jump the switch on the ACC system, the compressor will not cycle on. If this happens, you will need to disconnect the battery for about 30 sec to clear any retained memory from the ACC & PCM. After you hook the battery back up and start the car, the compressor will run for a while until the controller starts going through its self-diagnostics. If faults are found, it will usually shut off the compressor again. Usually though, you will have plenty of time to add Freon while it is doing its self-diagnostic thing. Be prepared and have the gages hooked up to the lines and the Freon container ready to charge, then all you have to do is open the valve.