1. If the thermal switch at the base of the radiator is damaged, the most likely failure is an open circuit. The fan motor does not turn on even if the refrigerant reaches operating temperature.
2. To check the thermal switch, disconnect the electrical wiring, and connect the connector clamps. The fan must be running (even without the ignition on), in this case the thermal switch is defective and must be replaced.
3. Before removing the thermal switch, first drain the cooling system as described in Chapter 3.
4. Disconnect the negative battery terminal.
5. Disconnect the electrical wiring, unscrew the thermal switch from the radiator, remove the seal washer.
6. To check the operating temperature of the thermal switch, immerse it in a tray of water so that only the screw end of the switch is immersed, the electrical contacts must not be in water. Connect an ohmmeter between the switch terminals, or a battery and an incandescent lamp in series with the switch. Place a thermometer in the pan, heat the water, record the temperature at which the switch closes. Let the water cool and note the temperature at which the switch contacts open. If operating temperatures are not within the Specifications, replace the switch.
7. Install in reverse order, always use a new seal washer. Fill the cooling system as described in Chapter 5.
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