My car overheats with the a/c on at idle up until around 40mph or so. I've changed all the standard parts related to overheating. Runs about 220 max with a/c off at all speeds and with the a/c on the highway as well. I looked under the hood at idle when it was almost overheated and saw that my serpentine belt was trying to stop every few seconds for a quick burst. I haven't seen it again since that one time. What's funny is that the a/c works really well. Is my compressor clutch most likely the culprit whether it's trying to seize or just putting too much load on the engine? The belt looks fine even though this has been happening for months. Thanks!

 

A/C compressor cycles - this is normal. The clutch will engage, then disengage, then re-engage, constantly. When it's engaged, there is quite a bit more load on the system, more load equals harder work = hotter temps.

You might try adding some refrigerant to the system. Less refrigerant means it will cycle more to a point.

Is you fan running when A/C is on? The elctric rad fan should run always as long as the A/C is on. If it's not, then there might be an issue with that wire/switch that turns the fan on when A/C is on.

 

Yes I know about the cycling. While the compressor clutch was engaged something was trying to stop the belt from moving for a split second, as in it seemed that one of the pulleys on one of the accessories was locking up for a split second every few seconds. (the one time I noticed it doing this) The rad fan works properly.

Actually now that you mention it I don't recall hearing it cycle lately, only running constantly when the a/c is on. Maybe my newish Oreilly cycling switch has crapped out. I attributed it to the ambient temperature, pressure, etc. stats that control the different times the compressor disengages the clutch. I know sometimes in the past it would cycle every 8 seconds, sometimes every 20, etc. Wouldn't something explode if it didn't cycle off??

 

Well I think I might have found the problem. My compressor was not cycling it was staying on all the time with the a/c on. I screwed the cycling switch screw clockwise until it started to cycle but during the adjustments the screw must have stripped and returned to the constant on cycling. Hopefully a new cycling switch will do the trick. Thanks to Camaronewbie for saying it out loud so it clicked in my brain.

 

Just for fun, might want to check the smog pump and make sure the pulley for it spins freely - I have seen them seize up before - if the bearings in it are going bad that might be an issue as well.

 

Smog pump deleted!