How To Replace a Pool Pump Capacitor


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Save yourself the cost of a new motor. Check the capacitor first. When you turn on your pump and the motor produces a humming sound, the motor may be frozen so that it won't turn or you may have a bad capacitor. Check the capacitor. It can be replaced for a fraction of the price of a new motor. Note: Some motors have two capacitors: a run capacitor and a start capacitor. If so, check both.

Click Here to View Pump Motor Parts (Including Run & Start Capacitors, Bearings, and Switches) 


Step by Step


Step 1

Turn off the power to the pool pump. For maximum safety turn the power off at the circuit breaker.

Step 2

Depending on the make of the pool pump, the capacitor will be under a hump cover on top of the motor, or it will be under a cover on the electrical end of the motor, or both. Some pumps have both a run capacitor and a start capacitor. The run capacitor will generally be rated at 15-50 MFD and 370 VAC. The start capacitor will generatlly be rated at 50-400 MFD and 125 or 250 VAC. This picture shows the location of the capacitor under a hump cover.

Click Here to View Pump Motor Parts (Including Run & Start Capacitors, Bearings, and Switches) 

Step 3

This picture shows the location of the pool pump capacitor at the end. In either case the covers are normally held on with two screws. Remove these screws to take off the cover and expose the capacitor. This capacitor is about the size of a roll of half dollars.

Step 4

Pool Pump Capacitors store an electrical charge that can shock you even when the power is off. Before removing the capacitor, discharge this energy by placing a screwdriver across the leads of the capacitor. CAUTION: Capacitors have been know to explode when shorted out. For your protection wear eye protection and place a cloth over the capacitor before shorting it out.

Step 5

If the capacitor is located at the end of the pool pump, remove the single screw that secures a clip holding the capacitor. Note how the plastic strip is positioned between the clip and the capacitor. It will have to be replaced in this position to keep the capacitor from shorting out on the motor. If the pool pump capacitor is on top of the motor, it should be free after you have removed the cover and the capacitor's leads.

Click Here to View Pump Motor Parts (Including Run & Start Capacitors, Bearings, and Switches) 

Step 6

Remove the leads to the pool pump capacitor. Note the placement of the leads so that you can restore them to their correct position when you reconnect them.

Step 7

Check the rating on the pool pump capacitor for replacement specifications. They will vary by manufacturer. Look for their MFD (or uf) and VAC specifications. For example, this one is a start capacitor rated at 124-149 MFD and 125 VAC. Try to replace the bad capacitor with an identical capacitor. If the exact capacitor is not available, you can use one with slightly higher capacitance. Do not use one with a lower rating.

Click Here to View Pump Motor Parts (Including Run & Start Capacitors, Bearings, and Switches) 

Step 8

Use a multimeter to verify that the capacitor is bad. Using the lowest ohms setting, touch the meter leads to the pool pump capacitor's terminals. If meter remains at 0, you know that the capacitor is bad. Check the new capacitor to verify it is good. First short out the terminals on the new capacitor to reset it. Then touch the meter leads to the capacitor terminals. If the capacitor is good, the meter will jump up to the other end than slower back off to 0.

Step 9

Connect the motor leads to the pool pump capacitor and secure the capacitor in place as required. Watch the placement of the plastic strip as mentioned above.

Step 10

Replace the cover.

Step 11

Reestablish power at the circuit breaker.


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Anonymous  Posted: 4/20/2020 

My pump started smoking and popping.motor still turns b hand.

InyoPools Product Specialist  Posted: 4/24/2020 

If the motor turns by hand, that just tells you the bearings haven't frozen up. But if your motor is smoking and popping, that is an electrical issue. Have you tested any of the motor circuitry since the almost fire started happening? Reference: Using the Proper Test Equipment to Troubleshoot Pool Motors

 Posted: 1/29/2020 

I have a AO SMITH Century centurion with this data on the name plate. Cat B128 Serial 007083M Part 7-164303-23 Type CX FR M56J HP 1.0 SF 1.4 PH1 Hz60 RPM 3450 Volts 230/115 AMPS SF7.2/14.4 TIME CONT ENCL DP FORM KJM CODE J. It is in Nevis an island in the Caribbean. Can you advise on what capacitors to take down that are appropriate for this pump. Thanks in advance

InyoPools Product Specialist  Posted: 2/10/2020 

The replacement run capacitor for the B128 - 1.0 HP Round Flange 56J Full Rate EE Motor, is the 25 MFD - 628318-307

Anonymous  Posted: 1/5/2020 

I have a Century two speed motor - B984. It only hums when I turn it on low. It works fine on high. And it will run on low if I spin the motor or start on high and change to low. Could this be the capacitor?

InyoPools Product Specialist  Posted: 1/6/2020 

This sounds more likely a bad switch or governor issue than a resistor. Is this a new or old motor? Has it been recently re-wired?

Anonymous  Posted: 8/11/2019 

I have a Hayward super pump model # SP2607X10A and I was just wondering what run capacitor I would need?

InyoPools Product Specialist  Posted: 8/13/2019 

We would need to know the part, catalog, or model number of the motor to identify the motor. The SP2607X10A  is the pump housing model number.

 Posted: 7/20/2019 

I have a Pentair 340040 2hp pool pump. What run capacitor does it use? Thank you.

InyoPools Product Specialist  Posted: 7/22/2019 

340040  is the model number of the pump housing, we would need to know the model number from the motor label.

Anonymous  Posted: 7/10/2019 

I have a.o. smith ac motor number C48C34A72. I want to know which capacitor model i need to replace\

InyoPools Product Specialist  Posted: 7/11/2019 

That number does not cross-reference to a part. Can you verify that is the correct identification number?

 Posted: 7/9/2019 

I have an AO Smith 1.5 HP pump model C48L2N134B1. When first turned on it hums for a couple of seconds and then starts. I assume it's the Start capacitor which needs to be replaced. Can you let me know the part number. Thanks!

InyoPools Product Specialist  Posted: 7/10/2019 

The start capacitor for the UST1152 is the 161-193 MFD (BC-161)

 Posted: 6/19/2019 

I have a Polaris PB4-60 pool vacuum pump with a AO Smith motor 7-173840-23, Type: CS, FR: N56CZ, HP: 0.75, SF: 1.50 It’s doing the hum noise thing. Can you tell me if it has both a start capacitor and a run capacitor? Do you carry the start capacitor? Thanks so much.

InyoPools Product Specialist  Posted: 6/19/2019 

The B625 booster pump motor only has a start capacitor which is the 124-149 MFD (BC-124).

 Posted: 5/20/2019 

I took my capacitor off and when I came back the plastic had blown away. Is it okay to replace the capacitor w/o it being on there or is there something else I can use as a subsitute? Thx

InyoPools Product Specialist  Posted: 5/20/2019 

The motor can be installed without that plastic sheet covering the capacitor. Its primary function is to act as a warning label, stating the end cover should be screwed onto the motor before operating.

 Posted: 8/24/2018 

Hello Kelly - The booster pump motors only have a start capacitor. If you are getting proper voltage to the motor and the start capacitor is good, we recommend replacing the motor.

 Posted: 8/23/2018 

Does a booster pump have both a start and a run capacitor? I replaced the one that's mounted on the outside, but didn't think to look for another. When my pump is supposed to be running, there's no sound or anything. It doesn't overheat. I've turned the bolt head where the windings are and it moves freely. There's power actually getting to it, but nothing actually happens...

 Posted: 7/13/2018 

Hello Jacks - The run capacitor for the ST1152 is part number 5270-08. The start capacitor is part number 5270-11.

 Posted: 7/11/2018 

I have an AO smith st1152 model # K48M2N110c1. My motor hums when I turn it on but won't start. Can you give me the part number for the start and run capacitors? thanks

 Posted: 7/4/2018 

Just wanted to say thank you for this posting. Turned off motor for hour and a half and when I turned it on it just hummed. Thought my 4th of July was going down the tubes with no running pool and waterfalls all day. After reading this it took me one hour to get to the store and purchase a replacement capacitor and install it myself. Saved me about 5 days of waiting on a new motor and doing a motor replacement, plus it saved my 4th of July! Thanks!!!!

 Posted: 1/29/2018 

Antionio Anselmi - The capacitor is a good place to start. The start capacitor for a UST1102 is 5270-14.

 Posted: 1/28/2018 

Hello, First off, your site is amazing. I love that you genuinely want to sell people the correct product not an entire system. So, after reading comments I see that my pump when I turn power just quietly hums. Never starts up. Do you think that this is a start up capacitor issue? I have a century ust1102 1 hp motor on an in ground pool.

 Posted: 1/2/2018 

Caleb, The current run capacitor for B2853 is 2523057-001, 30 MFD, 440 Volt, 2” diameter. Older versions used a 30 MFD, 370 volt capacitor (5270-05) which was 1 ¾” diameter. Kit 10003946-001-001, has the 30/440 cap, with a larger housing to accommodate the larger capacitor. If you have the older capacitor, you can still substitute the larger 440V capacitor (with the larger housing). It is more resistant to voltage spikes.

 Posted: 12/31/2017 

Hello, I need a replacement run capacitor for a Century Centurion. Label states following info: Cat: B2853 Serial: 03413CH Part: 0-F56AA37A01-04 HP - 1 SF - 1.25 RPM - 3450 VOLTS - 230/115

 Posted: 11/13/2017 

Bret - I'd try replacing the capacitor first. That's the least expensive fix.

 Posted: 11/7/2017 

I have a top capacitor in the casing on top of the pump. Mine just blew off one day while it was running....casing and all was blown away from the pump. The capacitor was extremely hot, so assuming it overheated. Do you think I just need to replace the capacitor or do you think the motor may be damaged as well? Thanks

InyoPools Product Specialist  Posted: 8/28/2017 

ebv128 - Check that the new capacitors have the same specs as the original capacitors. Then retrace your replacement steps to see if there was anything else you may have done to affect the switch. Check the switch.

 Posted: 8/26/2017 

With the help of the video, I have replaced both the start and run capcitors on my Sundance Palermo 2005 2-speed emerson motor. However, now the first speed is not as strong as it used to be, and i need to push the button twice for the high speed to kick in and then off, and then on for the first speed to kick in. Sugggestions, please

InyoPools Product Specialist  Posted: 8/14/2017 

Anónimo - I'd try replacing the capacitor(s) first. You may have two capacitors, a run, and a start capacitor. They are the easiest repair. I can't help you much without knowing what pump you have. Do a search on our website for your pump. Once you find the pump's product page, look for the link to it user's manual. There should be a trouble shooting section at the end of the manual.

 Posted: 8/10/2017 

I have a pool pump that stopped working recently. There is a window on top of the motor where you can see how long it will run (2hr, 4hr, 6hr...24hr) and there is a timer button to select how long you want it to run and an on/off button. When the motor is plugged in, the light indicator for the hour selection blinks on and off, telling you that it is off. When you push the on/off button, it stops blinking (indicating that it is on) and the motor usually runs. The problem is that now, when it is plugged in, the light blinks and everything like normal, but when you turn it on, the light stops blinking but the motor doesn't run like it would usually do. There is no humming, no sound at all coming from the motor. The light indicator acts like it normally would, but the motor simply doesn't run or make a sound. Would the capacitor be the issue, or is it another problem. I can provide details if needed, please let me know and I hope to hear a response soon.

InyoPools Product Specialist  Posted: 8/7/2017 

Ed - If the motor is humming, it's a good bet that one of the capacitors is shot. Try replacing the start capacitor first, behind the back cover, then replace the run capacitor. on top.

 Posted: 8/6/2017 

I have a Hayward 2.5 super pump that quit while running, will not start and makes a humming noise. There is a capacitor on top is there also a capacitor behind the cover on this model. thanks

InyoPools Product Specialist  Posted: 8/5/2017 

Terrell - I did not receive the picture through this comment page. Could you provide the motor's CAT and Part # along with it's HP, SF and amps?

 Posted: 8/2/2017 

My capacitor went out, but my motor is only three years old. Here is a picture of the label: The Label reads:
Century Centurion
Switchless Motor
No Switch * No Governor

Can you tell me what kind this is and if so, do you carry it?


 Posted: 7/18/2017 

I have swimming pool pump that is being used as a well pump. I was told the electrical start component has went out. I would like to send you a pic but there is no option. My starter capacitor does not look like the ones you are showing. Do I need to replace whole unit?
I was having to plug it in everytime I used it. Then one day when I plugged it in, it went proof at the junction box.


InyoPools Product Specialist  Posted: 7/13/2017 

Anonymous (UST1152) - According to our motor rep: "The capacitor only sees one-half the circuit, so it can use the 110-125VAC capacitor".

InyoPools Product Specialist  Posted: 7/13/2017 

Anonymous (UST1152) - Thank you for your feedback. You make a good point. I will verify this with our motor rep.