How To Replace a Pool Pump Capacitor

Written by:  Danny Rhodehamel

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.

Tips & Warnings


Things You'll Need

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.

Comments (1 to 40 of 113)

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User: Inyopools

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.

User: PerplexEd

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

User: Inyopools

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

User: Sean

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.

User: Inyopools

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.

User: Inyopools

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.

User: wharton94

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!

User: Inyopools

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.

User: gunnyt

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

User: Inyopools

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.

User: Vana

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.

User: Em

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

User: inyopools

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.

User: wade

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

User: Inyopools

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".

User: Vern

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.

User: Inyopools

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.

User: TB DFW

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.

User: Inyopools

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.


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.

User: Inyopools

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.

User: Endlesspool single speed

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

User: Inyopools

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.

User: Mike Frank

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?

User: Inyopools

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

User: Mike Frank

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

User: Inyopools

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.

User: Jba750

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

User: Inyopools

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

User: scnellis

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!!!!!

User: Inyopools

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.


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.

User: Inyopools

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

User: Cliff

I have a hayward Power Flo Matrix with an AO Smith SP1510 motor less than 5 years old. All of a sudden it now hums. I have taken the back cover off and and can freely spin the motor with a screwdriver. I can't see a capacitor. I remove the 4 throughbolts and knocked off the electrical end of the motor. Still no capacitor. Now what? thanks

User: Inyopools

David - The capacitors we sell are at this link: Pump Motor Parts.

User: david

who know where to buy the capacitor

User: Inyopools

blown capacitor - The plastic cover over the capacitor provides insulation to isolate the capacitor from the metal cap. It should be screwed in place to make sure it doesn't slip off. See our guide on "How To Replace AO Smith Motor Parts - Overview" for an explanation of how the Start Switch and Governor, which engages the Start Switch, are supposed to work.


I replaced the motor on a similar motor. Same specs as the previous capacitor. My first question is. The the plastic cover for the capacitor have to be screwed in place? Does it provide some sort of ground? Also. I'm not sure what you call it. But is there a chance the V shaped part(sorry in a novist) isn't disconnecting once contact is made? The replacement capacitor blew when I replaced it.

User: Inyopools

John M - Yes, a humming sound is generally a good indication that the motor start capacitor is going bad. You may be able to get it going by tapping the electrical end of the motor, but I would look at replacing the capacitor.

User: John M

Yesterday my pump was running fine. I cut it off to backwash. When I cut it back on it would not start up. It just makes a humming noise. Could this be a capacitor problem? Thank you for your help.

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Tips & Warnings

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.

Discharge the pool pump capacitor before removing it to avoid a shock.

Disconnect power to the pool pump motor at the circuit breaker before working on the motor.

Please Note:

Inyo Pool Products is not responsible for any injury or damaged equipment
while using our guides. Using our guides is doing so at your own risk.
These guides are suggested use of your pool or spa equipment and may vary
depending on which product you are using.