Compressor Speed Sensor: Description and Operation

Compressor RPM Sensor (L4):

PURPOSE

The RPM sensor which is located at the rear of the refrigerant compressor, measures the speed of the compressor.

CONSTRUCTION

The RPM sensor consists of a magnetic core and a coil.

OPERATION

When the A/C system is engaged, compressor rotation causes an alternating voltage to be induced in the coils of the RPM sensor. The frequency produced by the alternating voltage informs the compressor cut-out control unit of the compressor speed. If the compressor speed differs more than 30% from that of engine speed, the compressor cut-out control unit considers the compressor to be jammed (overcharged or internally damaged parts) and current to the electro-magnetic clutch will be disengaged to protect the common engine drive belt and accessories.