Attic Fan Motor Not Working High Speed

A two speed attic fan should just need a basic toggle switch.

Attic fan motor not working high speed.

If this fan has a timer and or a variable speed switch repairs are sometimes possible if the fault lies in one of the switches and not the motor. Remove the outer casing of the attic fan and check to see if the belt is sagging cracked worn or broken. Attic fans can sometimes start making noise whether it s humming rattling or making some other annoying noise. 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.

Other possibilities include damage to the wiring or a switch best repaired by an electrician. Attic fan not turning on. If this is not your issue the next thing in line is the high speed relay mounted on the front of the hvac box behind the accumulator. Repairs are generally impractical.

If there is any damage to the belt replace it with a new one. If the motor is working but the fan blades are not moving the problem may be the belt. This means that the current running through the blower motor and its speed is therefore controlled by the resistor value. 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 that a whole house fan is receiving electrical power when it doesn t work at all. The user chooses a fan speed by selecting a speed which then connects one of the resistors in the blower resistor pack. Attic exhaust fans power ventilators we usually simply replace the entire unit. Little or no airflow.

Try tapping on that relay to see if it is stuck. It selects one fan winding for slow or the other for high. Does the speed switch look like the silver handle coming out of the plate. Blower resistors are made of.

When running at a high speed setting does the attic fan run hard or sluggishly. The blower resistor is connected in series to the blower fan motor. 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 this doesn t fix the problem a burned out fan motor may need replacing.

These are the common causes.