A/C Compressor clutch does not engage
 

The A/C compressor clutch on my '83 944 does not engage when the dash control is turned on. Warm air blows out the dash vents and the radiator cooling fan comes on. The system has a very low charge, still R-12, with no apparent leaks.
How can I check the operation of the clutch? Does the low pressure in the system affect the engagement of the clutch?:confused: All suggestions appreciated.

Yes it does! Low pressure in the system will effect it, there is a low pressure switch controlling it to engage and also there is a high pressure switch to cut it off. Small diameter pipe is high side and the larger one is low side. Low side fitting is on the compressor and high side fitting is behind the left head light. That is for 83 944's up to 85 I believe.
Good Luck

Bud

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87 930 black
86 951 black
87 944S White
83 944 N/A black
83 944 N/A white Auto
86 944 N/A part car
07 Armada
07 Mazda3

yes, the low pressure switch protects the compressor from being ruined if a leak occurs. I'd be willing to bet you have a leak, but you can send 12v straight to the compressor to find out if the clutch is bad. Please do not run the compressor this way for more than a few seconds, it will burn it up.

The schrader valves are the most common source for a leak on any a/c system. Your low is on the compressor, the high is at the drier behind the driver's side head light. Front seal leaks on the compressor (or any other place for that matter) render a black oily residue.

Thanks matt.
Can I charge the system without the compressor actually running?
Tom.

You should be able to get enough refrigerant in the system to allow the switch to function as it should and have the clutch engage on the compressor. It will cycle some (a lot at first, then less frequently) until it sucks in all the freon needed.

you can pull the rubber cover off the wires on the low pressure cut off switch & jump the connection with a screwdriver to get the compressor to kick on.
The low pressure switch is behind the drivers side headlight on the aluminum can looking thingey.
you will need to have the headlight up to reach it.
don't run it like that for more than 5 seconds at a time, but as you are filling the system you can remove the screwdriver from the terminals & it should continue to run as soon as the pressure is going up.

You can also bypass the low pressure switch (for testing the compressor) just by unplugging the compressor and giving it 12+ volts. My compressor never worked and it ended up being a clutch solenoid. Since clutch solenoids are so damn expensive, I bought a new compressor.

I'm with Matt...shouldn't ever be a reason to bypass that switch if you have done the work correctly. The safety measures are there to protect your compressor but still allow you to work on the system without bypassing anything. Probably in your best interest to use them.

OK, I hope I didn't burn up the compressor, but the clutch engages with a jumper wire across the wires to the low pressure switch. I ran the engine and turned the A/C switch on for just a few seconds, then turned the A/C switch off.
Also, sounds like ES12a refrigerant from EnviroSafe is the way to go to recharge the R12 system. Can you get it from any local parts stores?

Regarding ES refrigerant, you need to order it from the manufacturer.

An alternative is to find some Freeze 12 in a local store, but I don't think that F12 is quite as flexible.

Keith

Before you start looking for refrigerants, you need to find the leak(s). I'd at the very least, change both the schrader valves on the compressor. It's just a bike tire valve, you can find them anywhere.

How much freon do you have in the system?

SmileWavy Matt: PM

Don't see one.

Maybe went to your email?

got it, sent back your way.