AC compressor cycling

[Boxstard]

My AC works fine, it can keep interior cold, but I never hear the compressor cycling off and on to keep it to the set temp. It just stays on all the time unless I turn off AC, as if temp. modulation is only done by the blend door?

This is different from my experience with other cars which you often hear the AC compressor clutch turns on and off as it adjusts the output. My Saab turned the compressor disengaged at WOT to help acceleration that I consider rather P-car thing but my 986 does not do it.

Is it normal or maybe my AC system has something wrong? No big deal as I rarely turn AC on but this makes me wonder.

[dghii]

Here's how I see it...
Living in FL, I always select a temperature (LO) and fan setting to cool my car. I can't say I actually pay attention to my compressor cycling. If I was on a long drive and used the 'AUTO' function, I would expect to notice a cycle but if I was at highway speeds, the cycle may not be noticed.

Check vent temp with AC working. If in the 40's to low 50's, I'd bet you're good.

[Stl-986]

Your AC shouldn't cycle on/off. If worried I would hook up a set of gauges to check the high & low side.

With that said the 944's I owned would cycle it on & off. With the 986's I have had though it wouldn't cycle like this.

[Boxstard]

Originally Posted by Stl-986

Your AC shouldn't cycle on/off. If worried I would hook up a set of gauges to check the high & low side.

With that said the 944's I owned would cycle it on & off. With the 986's I have had though it wouldn't cycle like this.

If it is designed not to cycle on and off, temp is only modulated by blending warm air from heater core? It seems inefficient to keep the compressor loaded all the time, even after it gets cold enough to blend warm air, when it can get shut down.

[Stl-986]

Dont disagree. Have 2 986 in the driveway right now and both stay on all the time and ac blow ice code and pressures are where they are supossed to be.

[paulofto]

My compressor doesn’t seem to cycle on and off but the clutch engages and disengages regularly keeping the temp steady. I would think if the fluid was always flowing you would get a frozen expansion valve. Maybe an HVAC expert will chime in here.

[Boxstard]

Originally Posted by paulofto

My compressor doesn’t seem to cycle on and off but the clutch engages and disengages regularly keeping the temp steady. I would think if the fluid was always flowing you would get a frozen expansion valve. Maybe an HVAC expert will chime in here.

When I say the compressor cycling on and off, it really means the clutch engaging and disengaging.... that I never hear with my car once AC is turned on. It blows cold air and temp can be modulate, but apparently the compressor is always running.

[Blue99]

There are two types of compressor one has a clutch on the front - the click you can hear as is ‘cycles’ the compressor the other has an internal valve like a butterfly which does the same thing but you can’t hear it
All compressors cycle.

[Boxstard]

Originally Posted by Blue99

There are two types of compressor one has a clutch on the front - the click you can hear as is ‘cycles’ the compressor the other has an internal valve like a butterfly which does the same thing but you can’t hear it
All compressors cycle.

My car is 1997 and I do not think the compressor is variable displacement type, so that modulation can only be done with the clutch.