AOA all. my brother bought a coure cl couple of months back and installed A/C in it last month. today when he started the car and switched on the A/C there was this 'screeching' sound coming from the engine. and the sound increases if he presses the accelerator pedal. can anyone guide me as to what the problem is here. if the fan is switched on then there is no sound but as soon as A/C is turned on then noise starts coming. kindly help me.