everytime you swith ON the a/c unit of your car, the A/C compressor magnetic clutch engages with the pulley, producing the "click" sound. Pero di gaano maririnig ito, unless talagang pakikinggan mo. Kung ang setting ng thermostat mo ay masyadong mababa (CCW masyado), you will notice na more frequent yung 'click' sound na maririnig due to the engage/disengage action of the magnetic clutch. Adjust ng konti CW direction para mas malamig at less frequent ang engage/disengage action.