The thermo fan switch when it reaches its designed temperature is designed to switch on and when it reaches a lower temperature, it is designed to switch the power off. The thermo fan switch receives power from the fuse box. When it reaches a temperature the switch will bridge the terminals thus turning the thermo fan on.
THINGS TO LOOK FOR
Check that the connections are secure and observe that the thermo fan is switching on and off. Sometimes this may not occur and just manipulating or wiggling the terminals may cause the fan to switch on. If this is the case then take the terminal off and clean it and refit it. Otherwise replacing the switch might be another option.
IS IT EXPENSIVE TO REPAIR?
A thermo fan switch is a costly item at around $60.00-$90.00. It’s better to buy the same type of switch as the original.
TEMPORARY REPAIR AND LONG TERM REPLACEMENT
If stranded the switch may be bypassed and the terminals bridged, but remember this will put a load on the battery and will always turn the fans on when the ignition is turned on. Or on some vehicles, if you bridge the terminals it may stay on indefinitely.