[Alan Bush]

I'm starting the process of getting my a/c working. first thing, the compressor will not engage. is there any way to check if the compressor is bad. I was told the compressor will not engage if its out of freon, but I'd like to know if its bad before installing freon, if possible

 

[rrgrassi]

You can bypass the switch on the dryer. Do this with the engine off. You sould be able to see and hear the clutch engage. It is a GM POS R4, and they are not known for thier reliability.

Need more info on your current set up, like was it converted to 134, what has been replaced so far, etc.

 

[DOUGLAS MARTIN]

First - check for leaks in system. An air conditioning/radiator shop can pressure test as well as perform a chemical test with a 'sniffer'. If there are no leaks - where DID that charge go? - and your compressor is in good shape - sadly highly unlikely - you can get a charge and cool off. The system has plenty of o-rings and fittings and hoses that fail - the expansion valve is under the dashboard on the passenger side. By removing the lower dash panel you can gain access and reduce the time needed to check. Odds are the compressor is history - the coolant suspends lubricating oil and a leak usually blows the seals and bearings. Replacing the compressor is one of the least pleasant do it yourself projects a W123 offers, only slightly less unpleasant than paying a shop $$$$$$$

 

[mountainredneck]

anybody know about what a new one would cost? my bearing went out on mine and the lady i bought it from said she just had it charged. so , i doubt i will gamble on it. would one from any chevy work as long as it is an r4?

 

[carnut1]

The GM unit will look the same but will differ regarding metric threaded fittings and possible pulley differences. If she said bearing failed its a good possibility that the bearing in the clutch failed, not the compressor bearings. Its worthwhile to by pass the pressure switch on the drier to verify if in fact the compressor has truely failed.

 

[mountainredneck]

yes it is the clutch, i failed to say that in the post. so, would you go ahead and put a clutch bearing in it?

 

[carnut1]

That decision is yours. Are you keeping the car a long time? if so, replacing the compressor will provide added assurance that you wont deal with the system again anytime soon. The bearing replacement can be a bugger! First finding the bearing then finding someone with the proper tools to replace it.

 

[p100]

To test the compressor, do the following:

1. Rent A/C gauges from Auto Zone and connect to the low and high pressure fittings. See what the pressure is in the system. The static pressure with the engine not running should be at least 50 psi for a properly charged system.

2. Is system is charged, check the A/C switch, A/C thermostat switch, and the A/C relay. Any one of those may cause the clutch to not operate. Then, is no problem found here, check the supply voltage on the compressor clutch wires. If 12 V is present, and clutch still does not engage, check the resistance of the clutch with an ohmmeter. You should see about 2-5 ohms if the clutch is good. A burnt out clutch will have infinite resistance (=no continuity in windings).

 

[ku4rt]

Hey, I just fixed mine. Some previous owner had the system retro fitted for r134, so didn't have to mess too much with that. There was a leak in one of the valve stems on the low side. Pulled a vacuum and refilled (including compressor oil). Took all of about 45 minutes! The only problem now is the thermostat dial in the cab obviously doesn't work. I can turn it to 85 deg and it doesn't produce heat or cut the compressor off. ??? I hope it is just a bad variable resistor, but haven't had the time to check it. Anyone know the range of the var. resistor attatched to the dial is supposed to be?

 

[hempev]

For those with an original R-12 system, you can get a "Section 609 certification" that allows you to buy and install freon. The testing cost me $15 on-line, and all the parts needed for a refill (including leak-stop, lube oil, and 3 - 12oz cans of Freon) cost $125 off eBay. It was nice to hear the faint loading of the engine as the AC clutch kicked in that first time!