I have been trying to figure this out for a little while and about to check into the nutty house!! The Condenser fan went bad in my AC Unit. It was a 3 wire motor. I got a Universal replacment motor and installed it. The orginal Motor was a emerson 1/10 HP 1 Phase. The AC unit has a 35+5 Capacitor with a Extra Start Capacitor. The replacement motor is a mars 10468 multi-HP 2 speed reversible. Here is the noodle cooker. I have the white wire hooked to line. The black and red wires from the fan determine the speed of the fan, red for LOW and black for HIGH. I am only using the black because i need the motor to run on high to match the RPM of the original motor. I have the brown wire connected to the fan side of the duel CAP, with the brown\white strip wire unhooked and wire nutted. When I manually start the unit by pushing the contactor down, everything starts and the fan runs in the correct direction. when I turn the thermostat to cool and it kicks on, the fan runs backwards. HELP!!!!!
Lennox AC condenser Fan running backwards
hvac
Best Answer
Your capacitor is too small. The new motor you list requires a 10 MFD capacitor to run at 240 VAC. Since the OEM capacitor in the unit is only 5 MFD, the new motor will randomly run backward and it will run with far less than its rated HP.
Also, you should connect the new motor to run on LOW (red wire). These universal replacement condenser fan motors are not really multi-speed motors. They are actually multi-horsepower motors. At the low setting, your new motor is 1/5 HP. The OEM motor was 1/10 HP, and the fan blades for your condenser are sized for the 1/10 HP motor. When you install the correct new capacitor for your new motor, I think you will find that your condenser fan runs faster with the new motor on LOW than it did with the OEM motor.