Camry A/c Idle Problem

[richkuan]

Hi,

When I turn on the A/C, the engine rpm drops to around 500, it holds there for couple seconds then dis-engages the compressor and the rpm goes back to 800, then the compressor engages again, then disengage, and it keeps going on like this (800 - 500 - 800 - 500.....). The A/C runs great on highways. I know the idle should go up to compensate the extra load from the compressor. I checked the "Idle-up" from the service port, the rpm did go up to 1100 rpm as specified in the manual when the 2 ports were short-circuited. What could be wrong?