Radiator Cooling Fan Temperature Sensor / Switch: Service and Repair

DESCRIPTION

The electric cooling fan is controlled by a thermo switch, a relay and on models equipped with A/C, an air conditioning relay.
When coolant temperature reaches approximately 194°F, the thermo switch contacts close, actuating the fan relay which operates the fan motor.
During periods of A/C operation, the radiator cooling fan and the condenser cooling fan will operate regardless of coolant temperature.
When coolant temperature drops below a predetermined temperature, the switch contacts opens, shutting off the electric cooling fan.

THERMO SWITCH

Replace

On 1984-86 Sentra and Pulsar exc. turbocharged models, the thermoswitch is located in the radiator lower tank. On 1984 Pulsar turbocharged models, the thermo switch is located in the radiator right side tank.
1. Disconnect battery ground cable.
2. Drain cooling system into suitable container.
3. Disconnect thermo switch wiring, then remove switch.
4. Reverse procedure to install.

Fig. 1 Testing thermo switch (typical):

Testing

1. Remove thermo switch as outlined above.
2. Connect suitable ohmmeter across switch terminals, then immerse lower part of switch in water, Fig. 1. Ohmmeter should indicate an open circuit.
3. Place thermometer in water and heat. When water temperature reaches approximately 193°F, switch contacts should close and the ohmmeter should indicate continuity.
4. If switch does not operate properly, replace it.