How To Replace a Pool Pump Capacitor

WRITTEN BY:  Inyo Pools

  3.68 out of 5 stars on 28 ratings
(Click on a star to add your rating)

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.


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.

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.

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.

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.


(1 to 40 of 120)

Inyopools  Posted: 12/12/2016 10:41 AM  Inyo Product Specialist

Pumpprob - Generally, a whining motor does indicate your motor bearings are starting to fail especially if you have an older pump.

Pumpprob  Posted: 12/07/2016 13:12 PM 

I have a pentagram pool pump system...the motor is making a whining noise and is hot to the this bearings?

Inyopools  Posted: 12/05/2016 13:37 PM  Inyo Product Specialist

Raymond - Your K48M2P105B1 motor has two capacitors: the run capacitor is on the top under the bump. The start capacitor is under the cover in the back of the motor. The start capacitor is part number 2509516-002, 64/77 MFD, 250 volts. The run capacitor is 2522881-001, 35 MFD, 440 volts.

Raymond  Posted: 12/03/2016 18:23 PM 

I have a Sta-Rite (AO Smith) motor K48M2P105B1 2HP hot tub motor;
the run capacitor is 35 microF 370VAC but the numbers smugded off the start capacitor when I touched it. Can't find a lookup table for the motor and hoping you know. Thanks

Inyopools  Posted: 10/12/2016 23:16 PM  Inyo Product Specialist

ComFuzed - From your description, I would say that a bad start capacitor is likely. I'd replace it. It's relatively easy and inexpensive.

CornFuzed  Posted: 10/11/2016 22:23 PM 

Not sure at all if this is just a capacitor problem (close though)
Sta-Rite pump and motor (AO SMITH). Back-end of motor is a dead ringer for the Hayward in the pics above.
Capacitor 161-193 mF 110 VAC
(Not an AC person, lots of experience with DC)
1. Motor will not start, but growls (not what I'd call a "hum", but maybe lack of experience)
2. Cracked the pump and checked the impeller cavity (empty) and it spins freely using two fingers (so I have not disassembled the wet end) nor do I see or suspect a leak of any kind.
3. Resistance check on the capacitor jumps to 10-15K then slowly to infinity (not a jump to zero as some sources say, but my meter only goes up to 1K range).
4. Wiring conduit is aged and was actually cracked open in spots when I inspected it, but I saw no sign of corrosion/water damage on the connector or the wires.
5. Failure only started after an extended (clear weather) power outage (3 hrs). Don't really know if there was a spike before it went out since just about everything else in the house has protection (Florida ... lightening ... need I say more?)

So, original question, is this likely the capacitor?

Oh, one other thing. The plastic guard on the cap. was browned (heat damage?) and the outer casing of the cap. looks "rough" near the end away from the contacts (matches position of browning on guard) Would the cap. have acted as surge stop?

Thanks for any advice you can give me!

tealretired  Posted: 09/15/2016 13:28 PM 

Power company changed out meter yesterday - took several seconds for everything to come back up. Pool pump hummed when I turned it on this morning - used your website to troubleshoot. Local pool supply had the correct part in stock - about a minute to change out the part and pump started and runs fine. Many thanks!

Inyopools  Posted: 08/15/2016 12:04 PM  Inyo Product Specialist

PerplexEd - Sounds like a bad start capacitor. Try replacing the capacitor. If that doesn't work, you may have a dead spot in your motor windings and you would generally have to replace the motor.

PerplexEd  Posted: 08/13/2016 12:32 PM 

Pump run fine, makes a hard humming sound when trying to start,then kicks the breaker out. It will start after several attempts.

Inyopools  Posted: 07/25/2016 13:38 PM  Inyo Product Specialist

Sean - Many above ground pump motors do not have a start capacitor. It is likely that your Tidal Wave pump does not.

Sean  Posted: 07/24/2016 12:12 PM 

Thank you very much for the information. Can you let me know where the capacitor for a dual port Tidal Wave pump is located? My manual did not have it listed and could not find it anywhere on line. It is not located at the back the same as what this video demonstrates. Appreciate any help.

Inyopools  Posted: 07/06/2016 9:05 AM  Inyo Product Specialist

wharton94 - According to the motor rep: "The capacitor should be the higher voltage if it is to last, but would not make a difference starting the motor. A shorted winding, or a start switch may also be the problem". See our guide on "How To Replace AO Smith Motor Parts - Overview" for more information.

Inyopools  Posted: 07/05/2016 13:54 PM  Inyo Product Specialist

wharton94 - Humming is generally resolved by replacing the start capacitor like you did. I sent an email to our motor reps to see what capacitor they would recommend and if the windings could have shorted. Will get back to you.

wharton94  Posted: 07/02/2016 16:32 PM 

One day the high speed pump on my hot tub would only hum when I tried to turn it on. (It uses a 240v Emerson T55CXBNC-999 motor) After troubleshooting, I learned:
1.The motor shaft would turn freely (motor/pump were not frozen or jammed).
2. Spinning the motor shaft with a screwdriver (through the access hole) and concurrently turning on electricity to the pump, would fire up the motor and it would run just fine as long as needed.
3. Once the running motor/pump were turned off and subsequently turned back on again, the unit reverted back to simply humming only.

I pulled the motor and checked both the run and start capacitors - and found the latter was bad (which made sense). The original Aerovox start capacitor was rated 130-154 MFD @ 165VAC. I replaced it with your part #5270-12 which is rated 130-156 MFD @ 125VAC and reassembled the motor. But upon change...still just hums!
Now I'm wondering two questions:
1. Did I buy the wrong capacitor? The odd 165VAC rating of the original capacitor threw me a curve (especially since it is a 240 volt motor).
2. If the capacitor is probably not the issue, can a burned out winding allow the motor to run normally (once started), but not allow it to start on its own?

BTW, I want to throw you folks a huge kudo for maintaining this Q&A area on your website. It is a great source of information for DIY'ers like myself - and it's greatly appreciated!

Inyopools  Posted: 06/26/2016 12:52 PM  Inyo Product Specialist

gunnyt - Very sorry for the delay. This is our busiest time of the year and unfortunately, sometimes our calls and chats get backed up. We generally have a very good response rate.

gunnyt  Posted: 06/24/2016 10:45 AM 

hey guys what gives? im on live chat and i'm told have to check on capacitor will take a few min. 20 min later i get We're not around, but we'd love to chat another time

Inyopools  Posted: 06/21/2016 12:27 PM  Inyo Product Specialist

Vana - If you are replacing your current capacitor with one of a smaller diameter, it sounds like you are using a smaller rated capacitor. See Step 7. You cannot replace a capacitor with one of a lower rating.

Vana  Posted: 06/20/2016 16:12 PM 

How can you "buffer" the holding clip if the new capacitor is a smaller diameter than the old one? I tried bending the clip some but it wasn't enough. Thanks in advance.

Em  Posted: 06/19/2016 12:02 PM 

I wanted to say thank you for providing this resource! I have learned a little!

inyopools  Posted: 05/03/2016 11:46 AM  Inyo Product Specialist

wade - Sounds like you have a serious motor problem like shorted out windings. If you have had the pump for a while, it may be time to buy another one.

wade  Posted: 05/01/2016 16:01 PM 

my husband replaced the capacitor on our 2 hp inground pool pump and it blew up 2 separate ones . Old one pump didn't work at allis why replaced it

Inyopools  Posted: 04/15/2016 13:49 PM  Inyo Product Specialist

Vern 0- See our guides on "How To Troubleshoot a Pool Pump Motor - Motor Overheated" and "How To Troubleshoot a Pool Pump Motor - Motor Shuts Down".

Vern  Posted: 04/14/2016 13:23 PM 

My pool Jandy flopro .75hp pump is overheating and stops running after about 45 seconds then restarts after another couple of minutes. Is this because of a bad capacitor? If not what would you recommend.

Inyopools  Posted: 04/05/2016 11:47 AM  Inyo Product Specialist

TB DFW - The motor for your 2HP Pentair Superflo Pump is a B2748 and the run capacitor for that motor is specified for 30 MFD / 370V - our part number - 5270-05. You should be able to verify this by comparing it to the specs printed on the old capacitor.

TB DFW  Posted: 04/03/2016 23:07 PM 

I am having trouble finding the right size run capacitor for my 2HP pentair Superflo pump. Model number is ST-N1-2A/ 340040. Does anyone have a resource for this info.

Inyopools  Posted: 03/11/2016 10:26 AM  Inyo Product Specialist

foreclosure - I would try replacing the capacitor first. It's a quick and inexpensive fix. You might also consider changing the sand in your filter. When you start to clean out the green pool, remove the heavier debris out of the pool with a pool net or rake before running the pump so you don't clog the filter. Than go through the process in our guide on "How to Treat Moderate Swimming Pool Algae" to clear your pool.

Anonymous  Posted: 03/09/2016 23:15 PM 

I just bought a forclosure with an in ground pool. Would it be best to just replace the pump and filter since I don't know what I have? The motor only hums and the water is very green. It has a sand filter.

Inyopools  Posted: 11/06/2015 10:58 AM  Inyo Product Specialist

Endlesspool - I know of no way to cut a pump's rpm by reducing the electrical current flow. You might ask a motor repair shop, but I think you are looking at a major design change.

Endlesspool single speed  Posted: 11/05/2015 1:33 AM 

Is there any way to hack a 3/4 hp Pinnacle Pump to cut the rpm in half by reducing the electrical current flow?

Inyopools  Posted: 10/05/2015 14:30 PM  Inyo Product Specialist

Mike Frank - Yes. 610807-002 is the correct start capacitor for the C48L2N134B1 motor configured for either 115 or 230 V. When the manf installs the capacitor before shipping, they do not know if you are going to configure the motor for 115 of 230 V.

Mike Frank  Posted: 10/04/2015 20:40 PM 

Thanks, but that particular motor can be wired to run on either 115 or 230 and my unit is running on 230. The specs for the BC-161 capacitor say it is for 125V. Is that still the right capacitor?

Inyopools  Posted: 10/04/2015 10:32 AM  Inyo Product Specialist

Mike Frank - The proper start capacitor for the C48L2N134B1 motor also known as the UST1102 or UST1152 motor is the 610807-002 Capacitor.

Mike Frank  Posted: 10/04/2015 10:27 AM 

What is the correct start capacitor for AO Smith Motor Model C48L2N134B1?

Inyopools  Posted: 08/31/2015 16:05 PM  Inyo Product Specialist

jba750 - If your pump was working on both speeds and recently stopped on low speed, I would check your switch. If this is a new system and the low has never worked, recheck your wiring to make sure you have two circuits. I don't know how involved your control system is but here is a link to "How To Install a 2-Speed Motor and a T106 Timer" that might help.

Jba750  Posted: 08/29/2015 19:23 PM 

I have an AO Smith 2 speed pump that works on high but not low speed. There is a slight click when I put it on low but it does not start until I turn it on high

Inyopools  Posted: 08/24/2015 14:55 PM  Inyo Product Specialist

scnellis - 80 MFD would be too high. I wouldn't go beyond the next size up: 55 MFD.

scnellis  Posted: 08/23/2015 11:46 AM 

How high is slightly higher? I have an 80 MFD with 370 vac/b and can I use that to replace an 50 mfd with 370 vac? Please help me!!!!!

Inyopools  Posted: 07/23/2015 11:49 AM  Inyo Product Specialist

burned pump wiring - If you bought this pump from us, give us a call at 877-372-6038. We may be able to replace it. Check to make sure that the pump's motor voltage configuration is the same as the supply voltage from the breaker box. I don't think we have the part connected to that yellow wire, and I would be reluctant to replace it without knowing what caused the burn out.

Anonymous  Posted: 07/23/2015 1:17 AM 

Yesterday I replaced my pump motor. It worked for about 5 seconds then popped and started to smoke. When I removed the cover I discovered one of the yellow wires leading to the capacitor was next to the spring and has been burned into 2 pieces. Is there anyway I can repair this. This is a brand new UCT1152.

Inyopools  Posted: 07/21/2015 13:32 PM  Inyo Product Specialist

Cliff - Many of the Above Ground and Spa motors do not have capacitors. Your motor windings may be bad.