Attic Fan Does Not Run On High Speed

Homes built after 2015 are required to have all ductwork sealed and tested for airtightness.

Attic fan does not run on high speed. Unfortunately homes built before 2015 may have very leaky ducts. If it is rotating slowly or not producing a lot of air in the high speed setting you may have a problem with the exhaust or intake. If the attic fan isn t turning on it could be an electrical issue a problem with the thermostat or the motor of the fan that s not working. You can fix this issue by turning down the settings or checking that the fan is getting enough air.

If you have leaky ductwork. When running at a high speed setting does the attic fan run hard or sluggishly. Little or no airflow. Attic fans can sometimes start making noise whether it s humming rattling or making some other annoying noise.

Remove the outer casing of the attic fan and check to see if the belt is sagging cracked worn or broken. If there is any damage to the belt replace it with a new one. Attic fan not running at top speed. You select which speed it runs at based on the switch position.

Attic fan not turning on. Parts can come loose or erode from high amounts of fan usage while turning the speed up to high can cause a persistent loud hum. Your attic fan may not be turning on because of an electrical problem like a tripped circuit breaker a blown fuse or a bad connection. Check motor current draw and compare with specs.

Most of those attic fan motors have two motor windings. For this you can use a 9 v battery a dvm and a 1 megohm resistor from radio shack. Check that the blade moves freely. Some info on the motor is needed.

Then after checking the capacitor for a short or an open measure its value.