How To Replace AO Smith Motor Parts - Overview

WRITTEN BY:  Inyo Pools

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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.

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 provide 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".

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 off 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".

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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InyoPools  Posted: 8/29/2018 

Hello Lisa - The B723 motor was discontinued. The replacement for your Magnetek B723 is Century model B653.

Lisa  Posted: 8/28/2018 

Hi, I have a Magnetek Century Centurion pool pump and I am looking for a replacement motor for it. Do you have this? Or can you tell me what else will work? Here is the info: CAT:B723, Part: 8-164717-04, HP 1.0, Type:CX, Volts:208-230/115, Amps:SF 6.4-5.9/11.8, RPM:3450, AMB: 50C, SF: 1.40, Time:CONT, Code: J, Encl:DP, FR:M56C, Form:KJM, Insul class: B, PH:1, Serial: B86-265, 1081 Pool pump duty mount horiz with vent holes down, thermally protected. other info near sku: E44549 LR4642 and near words copper conductors only is 174050-01 Thank you! Lisa

Matthew  Posted: 8/20/2018 

Hello Scott - unfortunately we do not have a wiring diagram for the capacitor. But if you have not yet disconnected the old capacitor, you can take a picture of the wire connections as they are now for referencing when installing the new capacitor. We have an article concerning the low-speed issue on dual speed pumps, give it a read: My Pool Pump Runs On Low Speed But Not On High Speed

Scott  Posted: 8/18/2018 

Hi do you have the wiring schematic for the capacitors on a B2982 AO smith century? Would one cause the pump to only run on high speed and not low speed? (run capacitor?)

Matthew  Posted: 8/3/2018 

The B852 uses two of the 203 style motor bearings. We have a motor bearing chart page and a few part diagram pages for pool pump motors. Plus, you can always contact us at 407-834-2200 or email to for help with finding motor bearings. We'll likely ask for a part, catalog or model number listed on the motor label; or, a clear picture of the label.

Joe  Posted: 8/2/2018 

Hello! I just replaced my 3/4hp pool pump motor and all of the gaskets using a rebuild kit. It's running great. The motor that I took out of service looks pretty good though ... just needs new bearings and a new end cap (square metal flange 56y) The motor is a Century Centurion B2852. Any idea where I can get the bearings and end cap for this motor?

InyoPools  Posted: 7/27/2018 

Hello Schrapnel - The K48L2PA105 would require two 203 bearings.

Schrapnel  Posted: 7/15/2018 

Hello, I am looking for replacement bearings for an A.O. Smith pump part number K48L2PA105. Can you please point me to the right ones? Thanks and God Bless.

Inyopools  Posted: 7/13/2018 

Hello Peter - The replacement for the C48M2EC11C3 is model Q1152. Unfortunately, we do not carry that motor.

Peter Haynes  Posted: 7/9/2018 

I need a replacement motor for an A. O. Smith motor # C48M2EC11C3. It also has a label on the motor # 0813010 It is a pump motor, 2HP, 120/230V 60 hz single phase, 3450rpm, SF 1.1, and has a square flange motor, 5/8" shaft with an impeller retainer screw in the end. Rating is cont, Thermally protected, Ambient 50 deg C, Max amps 24/12, It is for a SW pump. can anyone suggest a supplier to cross reference this motor please?

Inyopools  Posted: 3/5/2018 

Burel - I'm not finding your motor under C48K2EB23. Can you recheck the number and give me more information like Manf and model, a second model number, HP, SF Amps and FR.

Burel  Posted: 3/2/2018 

Hi I am looking for the references and prices of the bearings and the starting capacitor for a referenced motor : C48K2EB23 Regards Marcel

InyoPools Product Specialist Dennis R.  Posted: 9/25/2017 

Frustrated with pump - Here's another guide that goes into more detail on windings, "How To Use a Multimeter to Test a Pool Pump Motor - Winding Resistance".

Frustrated with pump  Posted: 9/23/2017 

Thank you for the reply. I checked the guide on "How the Common Capacitor Start Pool Motor Works". Didn’t see anything in there about the windings and how to check if they have shorted out. Please help.

InyoPools Product Specialist Dennis R.  Posted: 9/23/2017 

Frustrated with pump - Check for continuity on your motor windings. They may have shorted out. See our guide on "How the Common Capacitor Start Pool Motor Works".

Frustrated with pump  Posted: 9/22/2017 

I’m also having an issue with my AO pump motor. Mine is connected to a pump for the sprinkler system. I have tested the pressure switch, checked voltage and replaced the start capacitor. Still nothing. No humming, clicking or anything. Motor #C48K2PA105 Any thoughts? I cleaned the contacts on the switch and the pressure switch. Tried wiring it directly bypassing the pressure switch with no change. The shaft spins freely so it doesn’t seem locked up. What else should I check? I have removed it from the pump now. Is there a way to test it on the bench?

InyoPools Product Specialist Dennis R.  Posted: 9/17/2017 

Redleg44 - A capacitor is often discharged after the motor is off a while. This is more a safety precaution. Check that the governor is not stuck open. The thermal overload may be defective. Try replacing it. Also, check for a short(s) in your motor winding.

Redleg44  Posted: 9/16/2017 

I have a pool pump with an AO Smith model number C48L2N134B1 Motor. With the timer switch on it does nothing. No hum to hear or feel. There is 240 volts present at the terminal. The start capacitor looks OK; an ohmmeter reads no continuity (not shorted) but there was no charge on the capacitor when I attempted to discharge it before reading continuity. The start switch appears to be closed. The only thing I can think might be wrong is the thermal overload may be permanently open.

Your thoughts?

InyoPools Product Specialist Dennis R.  Posted: 9/7/2017 

Rusty75 - Unfortunately, we do not have instructions for replacing motor windings. It is my understanding that this requires special equipment and the tolerances required are not something most people would attempt. Usually, when a motor's winding had to be replaced, you'd take them to a motor shop, but due to relative costs, that's really done now.

Rusty75  Posted: 9/4/2017 

I have a Sta-rite 1.5 hours SNF-L pump. I have broken it down all the way and tested the windings as directed. I get an OL on my multimeter when I test L2 and Red (power & windings through start windings). So I believe they are bad. How do I replace the windings? The motor would turn on and hum while barely turning(maybe 5-10 evolutions) and then cut off after about 10 sec. Bearings are fine and nothing impeding it as the shaft spins freely.

InyoPools Product Specialist Dennis R.  Posted: 7/13/2017 

cuzy - Here are links to the three parts you requested for your motor, model #K48L2N104, aka CT1102.
front bearing - Bearing, 304 Ntn-6304-ll (6304) - $21
back bearing - Bearing, 203 (62032rs) (Single) - $21
fan - Essex Group Cooling Fan, Id 25/32in O.d. 4 3/4 In (saw-48) - $35
And the mysterious "How To Replace the Cooling Fan on an AO Smith Motor" is still in process.

cuzy  Posted: 7/12/2017 

Hmmm, so where is this mysterious"How To Replace the Cooling Fan on an AO Smith Motor" that you mention at the end of this document?

Wouldn't you know it, I just replaced my overheating AO Smith pump motor (thanks for sending me your excellent replacement Century motor, it works like a champ), and when I removed it from the pump, I discovered its internal cooling fan had self destructed.

I'm considering buying the fan and bearings, but I'd like to know the cost of all 3 items as well as availability (and part #s) for my old motor first. Its model # K48L2N104, serial 22310FM, 1HP SF 1.5 56J Frame motor.

Not sure if it is worth it to "rebuild" it with these 3 items, when I now have the new motor. Should I bother, just to have a "backup" motor?

Regards, Cuz.

Anonymous  Posted: 10/11/2016 

You discuss replacing the motor bearing[s] but no reference to size or where to purchase [including the seal. I've found the bearing but nothing about the flange seal. Some info on this would be very helpful. Thank you.

InyoPools Product Specialist Dennis R.  Posted: 7/13/2015 

novice - Yes the run capacitor (25 MFD /370 VAC) in on top of the motor under a bump. The start capacitor will be under the electrical cover at the back of the motor. The start capacitor will be rated between 50-400 MFD and 125 or 250 VAC. See our guide on "How To Select the Right Capacitor For Your Pool Pump Motor" for more information on pool pump capacitors.

novice  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?