Radiator Cooling Fan Temperature Sensor / Switch: Description and Operation

Coolant Temperature Switch (S25/11):

PURPOSE

The 105/120°C temperature switch activates the auxiliary fan via the high speed relay, and deactivates the compressor clutch via the compressor cut-out control unit to prevent engine overheat.

LOCATION

The 105/120°C temperature switch is located near the front of the cylinder head.

OPERATION

At coolant temperatures of approx. 221°F (105°C), the temperature switch activates the auxiliary fan (high speed), via the high speed fan relay. As the temperature drops below approx. 206°F (97°C) the circuit is opened and fan operation discontinues.
At coolant temperatures of approx. 262°F (128°C), the 120°C temperature switch disengages the A/C compressor via a ground signal to the compressor cut-out control unit. As the temperature drops below approx. 244°F (118°C) the temperature switch circuit is opened, reactivating the compressor.