Radiator Cooling Fan Temperature Sensor / Switch: Description and Operation

Coolant Temperature Sensor Location:

PURPOSE

The 105/115°C temperature switch (S25/5), which is located at the front of the cylinder head, is a dual function switch. One switch activates the auxiliary fan via the high speed relay to prevent engine overheat. The other switch deactivates the compressor clutch via the compressor cut-out control unit to prevent engine overheat.

OPERATION

At coolant temperatures of approx. 221°F (105°C), the temperature switch completes the ground circuit for the high speed fan relay, activating the auxiliary fan (high speed). As the temperature drops below approx. 206°F (97°C) the circuit is opened and fan operation discontinues.
At coolant temperatures of approx. 239°F (115°C), the temperature switch disengages the A/C compressor via a ground signal to the compressor cut-out control unit. As the temperature drops below approx. 226°F (108°C) the temperature switch circuit is opened, reactivating the compressor.