300SDL (126.125) L6-3.0L DSL Turbo (603.961) (1987)
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.