How To Replace AO Smith Motor Parts - Overview


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This guide provides an overview of the A.O. Smith motor parts that you can replace on the electrical end of your motor. This picture shows the electrical parts with the electrical cover off. Instructions for replacing each of these parts are referenced after the part description.

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Step by Step


Step 1

VIEWS PARTS - This picture identifies the replaceable electrical parts on a common A.O. Smith motor. Not all the A.O Smith motors will have all these parts but they are common to most of their motors. 

Step 2

CAPACITOR - This Capacitor, referred to as a Start Capacitor, is tied directly to the Start Winding. This Capacitor together with the Start Windings provides an increase of 150 -175 % of torque to the motor shaft during its initial startup. When the motor reaches 2/3 to 3/4 full speed after a few seconds of operation, the start circuit will shut off. The start capacitor will generally be rated at 50-400 MFD and 125 or 250 VAC. If your motor won't start and hums when you try to turn it on, you probably have a bad Start Capacitor.  For instruction on replacing this part see our guide on "How To Replace a Pool Pump Capacitor".

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Step 3

STATIONARY SWITCH - The Stationary Switch or Start Switch is commonly shaped as a V with contacts at the point of the V. When the motor is at rest, the contacts are pushed together by the Governor and the start circuit is closed ready to give the motor an extra boost to get started. If the contact points don't line up correctly, you may have to replace them. For instructions on replacing this part see our guide on "How To Replace the Start Switch on an AO Smith Motor".

Step 4

GOVERNOR - The governor controls the opening and closing of the start switch. When the motor is off, springs on the arm of the governor cause the arm to come in contact with the bottom of the start switch causing the two contact points on the switch to come together and close the start winding circuit. When the motor is turned on, the rotational force of the shaft causes the weights on the ends of the governor to spin out. When that rotational force is greater than the force of the springs, the arm on the governor drops down and the contacts on the switch separate and disconnect the start capacitor circuit. With age, the governor will sometimes stick open so that when the motor shuts off, the start circuit will remain open and the motor will not restart. For instructions on replacing the Governor see our guide on "How To Replace the Governor on an AO Smith Motor"

Step 5

TERMINAL BOARD - The Terminal Board provides contact points to connect wires your outside power source to the motor. If this Board is damaged you may have to replace it. For instructions on replacing the Terminal Board see our guide on "How To Replace the Terminal Board on an AO Smith Motor".

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Step 6

TERMINAL OVERLOAD PROTECTOR - The Thermal Overload Protector helps keep the motor from overheating. When the motor amperage exceeds max amps, the motor will overheat, and the Overload will shut the motor off until it cools. If the motor keeps cycling on and off, you either have a defective Overload or some other problem with the motor. To replace the Thermal Overload Protector see our guide on "How To Replace the Thermal Overload Protector on an AO Smith Motor".

Step 7

BEARINGS - With age or water damage the bearings in your motor may become worn or damaged to the point where start to screech. With the right tools, you can replace these bearings yourself. For replacement instructions see our guides on "How To Replace the Bearings in a Pool Pump Motor - Part I" and "How To Replace the Bearings in a Pool Pump Motor - Part II".

Step 8

COOLING FAN - A cooling fan is attached to the shaft of the motor to help cool the motor during operation. The fan is mounted just behind the front motor bearing. Occasionally the blades of the fan will be damaged and will need to be replaced. For instructions on replacing this fan see our guide on "How To Replace the Cooling Fan on an AO Smith Motor" (In process).

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 Posted: 7/12/2015 

if the motor has a start and run capacitor with smaller/ run capacitor on top (a 25/370) where is the other capacitor located?, in the back housing?