Air Conditioner Compressor Clutch

Old 05-29-17, 07:08 AM
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Air Conditioner Compressor Clutch

A mechanic installed a new aftermarket compressor clutch on my 1988 T Bird with 5.0 litre V8 two years ago. I got it out of storage, and I had no cold air, so I lifted the hood to see if the clutch was woking. It was moving sporadically like it was trying to engage, but not fully. What can I do without a shop load of special tools to free up this clutch. Fuse was fine, and the T-134 is in the green zone on my fill can guage. What happens if it goes into the red zone?
Old 05-29-17, 10:07 AM
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The DIY refill kits have minimal ability to diagnose problems with a system.
There are several things that can cause compressor short cycling and you need proper gauges and an understanding of how things are suppose to work to troubleshoot what is going on.
Old 05-29-17, 11:24 AM
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Jump low pressure switch or power clutch directly to see if clutch is good. Usually low pressure causes this.
Old 05-29-17, 02:17 PM
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Buy set of gauges at HFT. You have leak somewhere.
Old 05-31-17, 12:08 PM
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Charge, etc.

Most of the time it is an undercharged system that causes this, usually because of a leak. The leaks are often at the fittings, so try and inspect and see if you can see/feel oil around the fittings, and/or if they are accessible snug up the fittings a bit (not too much, there are o rings in there that will not do well to overtightening) wherever you can. If you see evidence of leaks then your system fill is no doubt low. An ac system should be clean and dry, no leaks at all. (This simple inspection approach assumes leaks are not in the compressor seals, or pinholes in the evaporator or condenser coils, but even then you can often spot some visual (ie. the weeping of oil that is in the ac charge) sign of the leak).

Since you are inspecting things, check the pressure sensor switch, make sure the wires and contacts are clean. It is not a big ticket item to replace, but does require the system to be recharged.

A/C Clutch Cycle Switch-Pressure Switch 4 Seasons 35960

From your description, it is possible the system was overcharged at the previous service, overcharging can also create system cycling like this. Since your system is not working, if you see no sign of leaks from your inspection might release a bit of the pressure as a last attempt and see if it helps. Since you ask about the can gauge being red, it might just be the ambient temperature effect on the reading, but could be an overcharge, but most important also a reminder to wear goggles when working around these systems, cans do burst from pressure spikes.

But, we are working blind here, the way to diagnose is to get the ac gauges for the high and low side, and read the pressures under various loads and temperatures. Only once this is done can one get more specific about where the problem might be (eg. could be debris or gunk moisture in the system and the dryer could be clogging). The gauge on the fill can is only part of the equation, those readings can vary widely based on ambient temperature, the high side pressure, and whether and when it is spiking, is important for diagnostic.

But overall, my guess is since you had work done, a fitting was just not snug enough and allowed a leak. Second guess is the pressure switch contacts are dirty. Let's hope it is something simple, as can often be the case on an older car.

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