How do you fix an attic fan that stopped working?
Short answer. To fix an attic fan, work from simple to complex: confirm power at the breaker and any switch, test the thermostat by turning it all the way down, check the motor and capacitor if it hums without spinning, and look for worn bearings if it squeals. Many fans are cheaper to repair than replace, but if the roof will be replaced soon, removing the fan may be the better fix.
Step by step troubleshooting
- Power: check the breaker and any wall switch. Some fans have a service switch near the unit in the attic.
- Thermostat: turn the dial to its lowest setting. If the fan starts, the fan works and the thermostat was set too high or has failed. If it does not, power may not be reaching the motor.
- Humidistat: on combination controls, a stuck humidistat can keep the fan on or off.
- Hum but no spin: often a failed capacitor or a seized motor. With the power off, spin the blade by hand; if it is stiff, the bearings are worn.
- Noise: squealing or grinding usually means bearings, and a rattling dome means loose fasteners.
- Solar fans: clean the panel, check its connection, and confirm it gets direct sun.
Safety first
Turn off power at the breaker before touching wiring or the motor, work in the attic early in the day, and step only on framing. If you are not comfortable with line voltage wiring, call an electrician.
Repair, replace, or remove?
- Repair the thermostat, capacitor, or motor when the housing and flashing are in good shape.
- Replace the whole unit when the dome is cracked, rusted, or leaking, or replacement motors are unavailable.
- Remove it when the attic has a ridge vent or adequate passive exhaust. A fan that competes with a ridge vent does more harm than good, and removal eliminates a large roof penetration.
If the fan comes out, the opening should be decked over and shingled in, not just capped. See roof ventilation basics and ridge vent vs box vents.