Hi All

Any ideas why the AC would cycle on and off repeatedly? This is an 88 GT Auto. I feel some cold air but there is something (compressor?) going on and off. Definitely can see the effect on the idle. Turn the AC off and the idle smooths right out. Car has been well maintained and AC was working before it was parked about a year ago.

Any thoughts?

Thanks

low freon - recharge and problem will be fixed

It's supposed to cycle on and off but a low charge will make it cycle more quickly.

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Dave

www.ltlfrari.com

quote Originally posted by steve308: low freon - recharge and problem will be fixed

I agree. The AC system has a low pressure switch. Since the compressor oil is carried via the freon, the system low pressure switch will disengage the AC compressor clutch (stopping the compressor). This is designed to save your compressor. When a system is even slightly discharged, this will happen.

quote Originally posted by psychosurfer: The AC system has a low pressure switch ... This is designed to save your compressor.

It's even more basic than that. The systems using the DA6/HR6 compressor, found in all Fiero V6es and some 4s, are CCOT (clutch cycling orifice tube) systems. Cycling the compressor clutch is how such systems adjust the cooling output to match the heat load. Protecting the compressor is only a secondary function of the pressure cycling switch.

I do agree that low refrigerant charge will cause the compressor clutch to cycle much more rapdily than usual ... every 3 or 4 seconds, rather than the typical 15 or 20 second cycle time.

The AC systems in some 4-cylinder Fieros use the V5 compressor, which is a variable displacement type that doesn't use a pressure cycling switch. In the V5 systems the only purpose of the low pressure cutoff switch is indeed to protect the compressor against loss of refrigerant.