Attic Fan Does Not Run On High Speed

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 fan does not run on high speed.

Attic fans can sometimes start making noise whether it s humming rattling or making some other annoying noise. When running at a high speed setting does the attic fan run hard or sluggishly. Remove the outer casing of the attic fan and check to see if the belt is sagging cracked worn or broken. If you have leaky ductwork.

Check that the blade moves freely. Then after checking the capacitor for a short or an open measure its value. Homes built after 2015 are required to have all ductwork sealed and tested for airtightness. Attic fan not running at top speed.

Little or no airflow. Attic fan not turning on. Most of those attic fan motors have two motor windings. Check motor current draw and compare with specs.

For this you can use a 9 v battery a dvm and a 1 megohm resistor from radio shack. 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. Running the fan when the air conditioner is not on could actually pull the heat out of the attic into the home.

High speed and low speed. I ve never heard of one that starts on high and switches to low. 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. You can fix this issue by turning down the settings or checking that the fan is getting enough air.

If there is any damage to the belt replace it with a new one.