Engine Speed Sensor: Description and Operation

Engine RPM Sensor:

PURPOSE

The engine RPM sensor which is located at the rear of the engine, senses flywheel rotation.

CONSTRUCTION

The RPM sensor consist of a magnetic core and a coil (monolithic sensor).

OPERATION

When the A/C system is engaged, flywheel 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 engine speed. If the engine speed differs more than 30% from that of compressor speed, the compressor cut-out control unit considers the compressor to be jammed (overcharged or internally damaged parts) and disengages current to the electro-magnetic clutch in order to protect the common engine drive belt and accessories.