When an attic fan quits or starts to grind, test it first, then match the new fan to the opening you already have.
To replace an attic fan, first confirm it has failed by checking power and testing the thermostat. Then shut off the circuit, remove the old fan, and install a new one that fits the same opening. Gable fans are the simplest swap: the CentricAir gable attic fan fits standard gable vents framed 16 inches on center and plugs into a grounded 120 volt outlet. Its manual says wiring should be done by a qualified person to local code.
Attic fans live a hard life, running through the hottest days of the year in a space that can bake. Eventually the motor wears out or the thermostat fails. The good news is that the opening, and often the power, are already in place.
Is the attic fan actually broken?
Check the power and the thermostat before you buy anything.
- Check the breaker or outlet.A tripped breaker or dead outlet looks exactly like a dead fan.
- Test the thermostat.On a warm day, turn the dial below the current attic temperature. If the fan starts, it works. Set it back to about 110°F, the setting CentricAir recommends.
- Listen to the motor.Grinding, squealing or a hum without spinning usually points to a worn motor.
How do you replace an attic fan?
Remove the old unit safely, then install the new one to the manufacturer’s instructions.
- Shut off power.Turn off the circuit at the breaker, and unplug the fan if it plugs in.
- Take photos.Photograph the wiring, thermostat location and mounting before you take anything apart.
- Remove the old fan.Disconnect the thermostat, unfasten the fan from the framing or roof, and lift it out.
- Measure the opening.Confirm the new fan fits. The CentricAir gable fan fits standard vents framed 16 inches on center; wider vents need framing down.
- Install the new fan.For a CentricAir gable fan, set it behind the vent, fasten the box to the studs and cover any open area of the vent around it.
- Mount the thermostat and restore power.Place the thermostat near the fan but out of the airstream, plug the fan into a grounded outlet and set the temperature.
What if the old fan was on the roof?
You can replace it with another roof fan, or move to a gable fan if you have gable vents.
A like for like roof fan swap reuses the existing hole and flashing when the sizes match. Switching to a gable fan avoids future roof work, but the old roof opening must be closed and sealed properly, which is a job for a roofer. Our gable vs. roof vs. solar guide compares the options.
What about the wiring?
Match the power to the new fan, and hire a qualified person for anything beyond plugging in.
Many older attic fans are hardwired. The CentricAir gable fan plugs in instead, and its manual calls for a grounded 120 volt, 60 Hz circuit with at least 14 gauge wire and 3 amps of available capacity, with no extension cords. It also says homes with a gas or oil furnace need the fan wired with a switch or interlocking device, and that wiring should be done by a qualified person to local code.
Should you replace it with the same kind of fan?
It is worth a quick check before you buy.
Swapping like for like is simplest, since the opening and wiring are already there. If your old fan was roof mounted and your home has a gable wall, a gable fan avoids keeping a hole in the roof. If what you really want is cooler bedrooms, a whole house fan cools the living space, which an attic fan does not.
The CentricAir gable attic fan fits standard gable vents and plugs into a 120 volt outlet.
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Frequently asked questions
How do I know if my attic fan is bad?
Common signs are a fan that no longer starts on a hot day, a grinding or rattling motor, or a fan that runs constantly. Check the outlet or breaker first, then test the thermostat by turning it below the attic temperature.
Can I replace a roof attic fan with a gable fan?
Yes, if your attic has a gable vent the new fan fits. The old roof opening then needs to be closed and sealed properly, which is a roofing job.
Can I replace a hardwired attic fan with a plug in fan?
Only if there is a properly rated outlet for it. CentricAir’s manual calls for a grounded 120 volt circuit with at least 14 gauge wire and says not to use extension cords. A qualified person should add the outlet.
Should I replace my attic fan at all?
If your attic runs hot, yes. A working attic fan keeps pushing heat out of the attic in any climate. When you replace it, check that the ceiling is sealed and the attic has enough intake vents.
Keep reading
Sources
- CentricAir, Attic Fan Installation Manual (PDF), uploaded March 2025, accessed Sept. 2026.
- CentricAir Gable Mounted Attic Fan product page, centricair.com, accessed Sept. 2026.
- U.S. Department of Energy, Building America Solution Center (PNNL), Attic Ventilation Fans, updated Sept. 21, 2022.