stickbow9

Hey everyone, I have looked for the answer through these posts but not quite found my questions answer. I have anew to me 1998 3.8 automatic which has a cycling AC clutch most of the time when the air is not on at the switch in my dash. I only noticed it because it happens during start up and occasionally during operation. Is this normal, or is this happening because I am more than likely low on refrigerant? AC seem to work fine. I noticed it because my car's idle would jump 500rpm for 2 seconds every 10 seconds....even for a 5 minute warm up before driving. Is this normal or am I hypersensitive to the sounds of a new car? Any help would be great.

Daehawk

If its off at the switch it shouldn't cycle on at all. And the coolant has no bearing on if it comes on or off. It would simply blow hot air if low or empty. FAIK

EDIT: I did have a car once that with the AC on it would drop RPM by about 500 when the AC compressor kicked in...if idling.

BabyGT

Actually there is a pressure sensor that prevents it from running if its to low I believe. Are you positive its the ac cycling? Might be idle surge from something unrelated to the ac.

One last thing to check. You don't have the defrost running right? That will cycle the compressor.

stickbow9

Thanks for the responses. BabyGT i did confirm that it was the AC compressor when it happened. I went out and saw the clutch engage followed by the engine rpms climbing and falling again after the clutch disengaged (drag on the engine causing it to rev?). I saw somewhere that someone had an AC clutch cycle switch go out. I will have to look at schematics, but at $12 I wouldn't mind if that was the culprit. Yes the AC compressor does engage when the defrost is on too. Thanks everyone I will continue to let you know what I find.

stickbow9

Well as it turns out, the switch position for "mixed" also cycles the ac compressor. So everything in my OP is ok, just as it should be. No cycling of the clutch when it should not. Thanks for the help.

BabyGT

I had a feeling the defrost was kicking on. Mixed runs the defrost cycle.