Attic Fan Does Not Run On High Speed

High speed and low speed.

Attic fan does not run on high speed.

Running the fan when the air conditioner is not on could actually pull the heat out of the attic into the home. If you have leaky ductwork. Then after checking the capacitor for a short or an open measure its value. Little or no airflow.

Remove the outer casing of the attic fan and check to see if the belt is sagging cracked worn or broken. Homes built after 2015 are required to have all ductwork sealed and tested for airtightness. For this you can use a 9 v battery a dvm and a 1 megohm resistor from radio shack. Most of those attic fan motors have two motor windings.

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. 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. Check that the blade moves freely. You select which speed it runs at based on the switch position.

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. I ve never heard of one that starts on high and switches to low. Unfortunately homes built before 2015 may have very leaky ducts. Check motor current draw and compare with specs.

Attic fan not running at top speed. If there is any damage to the belt replace it with a new one. 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. Attic fans can sometimes start making noise whether it s humming rattling or making some other annoying noise.

Attic fan not turning on.