Thermostatically Controlled Electric Fans: Testing

Disconnect fan motor wire connector and connect it with 14 gauge wire to a good 12-volt battery. If fan runs, motor is O.K., indicating car battery, coolant relay, coolant temperature switch, or A/C relay may be defective. If fan motor does not run when connected directly to a good battery, replace fan motor. For circuit diagram, see appropriate WIRING DIAGRAM article.