While attic fans are a great way to help keep a house cool if central air isn’t an option, attic fan motors tend to burn out quite often. To determine if the fan motor is broken, or if it is simply a connection problem, try the following steps.
WARNING: It is important to note that the following steps assume the attic fan has a circuit that can be unplugged from a receptacle mounted on the housing (a common feature on many attic fans). If the fan is an all-in-one system that is completely hardwired together, call a professional electrician.
Step 1 – Test the Fan Motor
Turn the attic fan off and unplug the motor from the thermostat. Once done, test that the motor still works by plugging the motor into an extension cord that is connected to an outlet. If the fan turns on, the motor is still good.
Step 2 – Test the Thermostat
Set the thermostat to "turn on" mode and plug a hand-held shop light into it. If the shop light turns on, the thermostat is working. If not, the thermostat may need to be replaced.
Step 3 – Test the Connection Between the Thermostat and the Power Source
Reconnect all the pieces of the attic fan and turn the device on again. Hold a non-contact voltage sensor near the wire leading from the thermostat to the power source. This device will demonstrate whether power is flowing through the wire, into the thermostat, and through into the motor. Follow the wiring as a far back to the power source as possible, checking for any place where the electricity may be stopping.