Why is my attic fan not working?
Short answer. An attic fan that will not run usually has lost power at the breaker or switch, has a thermostat set higher than the attic gets, has tripped its high temperature cutoff, or has a motor that burned out or seized. Solar fans most often stop because the panel is shaded or dirty or its wiring connection failed.
Work through it in order
- Power: check the breaker and any wall switch. Some fans are on a switch in the attic or garage that someone turned off.
- Thermostat test: on a warm day, turn the thermostat dial to its lowest setting. If the fan starts, it was simply set higher than the attic was reaching.
- Humidistat: if the fan has one, turn it to its lowest setting to see whether it triggers the motor.
- Firestat: many fans have a high temperature cutoff that shuts the fan off and, on some models, has to be reset or replaced after it trips. Check the manual.
- Motor: with the power off, spin the blade by hand. If it is stiff or grinds, the bearings are gone. If it spins freely but only hums when powered, the capacitor or motor may have failed.
- Solar fans: look for tree shade, pollen or dirt on the panel, and a loose connection between panel and motor.
Repair or replace?
Motors, thermostats and some solar panels can be replaced on their own. If the fan is old, its roof flashing is worn, or the attic also has a ridge vent, it may be better to remove the fan and close the hole than to keep repairing it. A dead fan still lets a little air out through its dome, but not much.
Safety notes
Turn off the power before touching wiring or the blade. Attics get dangerously hot on Georgia summer afternoons, so work early. Electrical repairs beyond swapping a plug-in thermostat belong to an electrician. See roof ventilation basics and ridge vent vs box vents.