With every car I’ve ever owned (with AC), when you set it to “Max” all it does is automatically recirculate the air. The compressor still cycles on and off. I imagine if the compressor were to run full time, it would eventually freeze up.
I’ve noticed cars doing both, running the compressor constantly and turning on and off. In my car, the compressor runs whenever the air conditioner is on. With recirculation on it gets painfully cold, even when it’s 110 degrees outside.
On earlier police cars, the Crown Vics, I could hear the compressor switch on and off while it idled. It happened fairly frequently, several times per minute. I don’t know why there are different kinds.
What don’t you understand about my earlier post. On every car I have owned since '65 the A/C compressor ran all the time it A/C was on. I noe have an '09 and I never notice it “cycling”. Also, running it on “Max” makes no difference to the compressor. It only changes the air flow from outside air to inside air.
EllyEllis:
What I don’t understand about your earlier post is that fixed displacement compressors were the norm through the early 90s, where manufacturers began introducing variable displacement compressors. Some might have been introduced in the late 80s - that’s not clear.
With fixed displacement compressors, the clutch was cycled on/off to keep the evaporator temperature in the desired range.
So if you’re saying you had older vehicles (that were equipped with fixed displacement compressors), I’m open to understanding how evaporator temperatures were controlled, if it wasn’t through cycling the clutch.
I don’t know anything abour fixed displacement compressors. I just know that the compressors in all my vehicles ran as long as the A/C was on. My '96 Dodge van did, and I even think my '09 Caravan does.