On my '82, seems my A/C kicks on, and just 5 seconds later, it's off already. Then, a mere 10 seconds later, it's on again. Is there a thermostat that needs moved, or a little tape?

It's low on freon.
The compressor kick off when the low side A/C pressure is too low. The oil in the A/C circulates with the freon. When the freon is too low, it can't carry oil to the compressor, and will cause damage. Also, the system won't operate and cool if the pressure is too low. That will actually cause the low side to freeze up, if it cools at all.
To prevent both of these, there is a low pressure cut-off switch to monitor the low side pressure. When the compressor kicks on the high side goes up, and the low side drops. If it drops too far from lack of freon, it will kick off the compressor. With no suction on the low side without the compressor running, the pressure quickly rises, the compressor kicks on, pressure drops quickly, the compressor kick off, and you get the rapid cycling.

Just add freon. Make sure you use the correct freon. R-12 or R134a. You may want to check for leaks, but up to a pound a year could be considered normal loss. Specs are 1/2 pound, but more in older cars is expected. Some systems will hold for years with out losing anything.

Ken Styer

|UPDATED|3/1/2004 7:35:08 AM (AZT)|/UPDATED|

I just had my air charged this weekend and the compressor does the same thing. Could it be a bad pressure switch, or would a low ambient temprature affect it also?

I would first question if it was fully charged. But yes, any compressor control switch could cause the problem. Not common, but possible. A low pressure gauge on the low side of the A/C will tell you right away. If the pressure drops quickly when the compressor comes on, it's low on freon. If not check the switches.
You could also have restriction in the system causing this by starving the low side for freon. This would cause it to act like low freon. The low side would still act like a low charge. The high side pressure would shoot up, then drop back off with the compressor running, if it runs long enough to observe this. If the system is full you would be able to see or feel a very drastic change in temp at the point of restriction. It will change at the orifice tube or expansion valve normally, but should not do this at any other point. Sometimes you will see frost at a restriction point. Sometimes you just need to feel for temp change. If you have a 60s or early 70s car it has a V.I.R. control set up. The problem would be in the V.I.R. if the system is full.

Ken Styer

|UPDATED|3/1/2004 3:15:03 PM (AZT)|/UPDATED|

Wow, lots of info. To add info, I have the same concern as Maint 1. My system was recharged last year right when I bought the car. This has been happening the whole time I've owned the car. It blows extremely cold when it's on an 'on' cycle.

Thanks again, just thought that if others were experiencing this, it could be a common factor, which Maint 1 leads me to believe it could be. Perhaps it's serious as you say Ken, when I get a chance, I'll see if a shop will give me a diagnosis.

Thanks !

Usually it's not too serious. If you have a bad switch it's not usually a big deal. Freon is easy. The very bad failures are not as common.
The fixed orifice type is what the newer C3s have, and they will cycle to some extent at idle and higher rpm, and be normal. This could be every minute or two to much longer, depending on ambient temp and operating conditions. The very rapid cycling is a problem.

Ken Styer

|UPDATED|3/1/2004 4:02:46 PM (AZT)|/UPDATED|

The temprature here in Vegas got up in the 70's today and the air conditioning compressor worked just fine. Ambient temprature was just too low the day I had the system charged. After all the time and money I spent this winter to get the air working I felt much better. The real test comes in about 4 months.

I should have added that. In cold weather the freon will contract, and the pressure will drop, acting like it's low. Pressure wise it is. Usually when the car has been running long enough, it warms up and expands, then operates okay.

Ken Styer