How To Replace a Pool Pump Capacitor

Written by:  Danny Rhodehamel
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 (3.67 OUT OF 5 STARS ON 27 RATINGS)

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

Video

Things You'll Need

Step by Step

Step 1
power pool pump

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

Step 2
pool pump capacitor hump cover

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
pool pump capacitor

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

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
pool pump capacitor

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
capacitor leads

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
rating on capacitor

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
pool pump capacitor

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 87)

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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.

User: 

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.

User: 

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.

User: Inyopools

jh47 - This is the wiring configuration for most Hayward capacitor motors with a thermal overload protector. I can't see from your picture if your motor has a protector or not. See "How the Common Capacitor Start Pool Motor Works" for a description of the electrical parts in a capacitor motor. Your wiring shows two yellow wires coming from the power supply and a white/red wire going to the switch. If you have an overload protector one of the yellow wire would be going to the #3 terminal on the overload protector. See step#7 in this guide, "How To Use a Multimeter to Test a Pool Pump Motor - Winding Resistance" for wires going to the capacitor. If you don't have an overload protector, your wiring is probably correct. I would take it back to the shop and have them test for a short in your circuit.

User: jh47

If the configuration of the leads in the image for Step 6 the correct configutation for all pumps/capacitors of that style?

Long story: I recently took my pump to the local pool shop to check the pump seal (all good), and they asked if I wanted the capacitor replaced. I said no, as long it looks good. I get it home, hook it back up and the capacitor blows immediately. Pop, smoke, oil, etc. So, I get a new one, and follow your instructions to replace it, but I hook up the leads the way they were arranged on the blown cap (see link to image below). Flip the switch and it blows the new cap too. So now I'm thinking the pool shop incorrectly re-installed the capacitor when it was in there.

Thanks.

https://lh3.googleusercontent.com/qtw9YiwAL6FRJCg0YQS-BWv1NlY0ftoA1z0Fgox5nQc=w560-h995-no

User: Inyopools

Blasttsunamisue49 - That's some handle you have! Your low tank water level is probably not due to the motor capacitors. When they are bad, the motor generally just sits there and hums. If you just added your third pump you may have introduced a suction air leak into your piping. Check all new connections to see if one of these is leaking. One pool owner did this by packing plumber's putty around each of the connections (outside) until the pressure went up. Then he knew which connection to replace. Also, you might check to see if any of the pump's impellers are clogged with debris. See our guide on "How To Clean Out a Pool Pump Impeller".

User: Blasttsunamisue49

What is wrong when the 3 2 speed pumps aren't pumping enough water into the filler to fill it up like it's suppose to do? Could it be faulty capacitors also?

User: Blasttsunamisue49

I have 3 2 speed pumps on my pool and the newest one is an A.O.Smithcorp UT21000CPP. It's not pumping enough water to fill up filter. What could be the problem? My other 2 pumps are Power Flo Matrix. Help me please. I have 2 kids and they live in the pool in the summer time.

User: Inyopools

Marc - You could start with replacing the capacitor. It's an inexpensive and easy fix. But your problem is more likely a damaged motor. When you run a motor dry for a period of time, it gets very hot and typically burns out the bearings or coils as well as some of the pump components.

User: marc

my pool filter housing cracked and water drained out. Went out side and pump was not working and was making a humming noise. turned it off,changed new filter system and now when i turn pump on it hums for a few seconds and cuts off. could it be the capacitor or motor bad?

User: Inyopools

Victor Newman - According to the motor manufacturer, the start capacitor for K48M2P105B1 is part # 5270-29 - 64/77 MFD, 250 Volt. 1 7/16" diameter x 2 3/4" long.

User: Victor Newman

Our above ground 2-speed pool motor hums when started on hi speed. It starts fine on lo speed. It is fine when switched from lo speed to hi speed. Pool guy says start capacitor is shot. There are no markings on the capacitor, too faded to read. He can't locate a start capacitor.

I read about a formula to find the correct capacitor: 2650 x FLA divided by supply volts. Our FLA is 10.0 and it is a 230v motor. It works out to 115 MFD. Our motor is a AO Smith K48M2P105B1, 2 HP, 3450/1725 rpm, motor# A100GLL-Y, Type T, Code G. 34107FM.

I have asked Century Electric 2 times for help. Nothing.

Any advice?

User: Inyopools

gmark – I don’t think it is the capacitor. A start capacitor is only operational on start up until the motor reaches near full rotation, and then it cuts out. So it wouldn't be cyclic unless the motor is slowing down periodically for some other reason. I would take the motor out of its housing and see if there is debris around the impeller or if the impeller is loose and rubbing against the diffuser. It may also be your motor bearings starting to fail.

User: gmark

Need help, I was hosing off my pump pad and my flo tech pump started making a loud humming sound and smelled like it was melting. This lasted 30 second s or so then started working again. It continues to cycle this wayour constantly every few minutes. Could the capacitor work intermittently

User: Inyopools

Pete – The majority of pumps use an A.O.Smith motor like the one shown in this guide. If your pump uses an A.O.Smith motor (see motor label), wire the capacitor as shown in step #6. If not, I would recommend calling the pump manufacturer.

User: Pete

Hi, I'm replacing my capacitor and don't know which terminals to hook the wires on because it's a different brand. How do I know which one to hook up. Can I damage the pump if I do the wrong one?

User: Inyopools

klst21655 - Sounds like either a bad capacitor or a short in the motor windings. If windings, you will have to replace the motor.

User: klst21655

My Hayward Super Pump makes a very loud buzzing noise when turned on. The Impeller turns freely but Pump will not run. Capacitator?

User: Inyopools

csitg - The "POP" would indicate something electrical. Take off the back cover of the motor and check the motor's capacitor (if it has one) and its thermal protector. See our guide on "How the Common Capacitor Start Pool Motor Works" to see where these parts might be.

User: Inyopools

Motor stopped - See these guides: "How To Determine Why a Motor Won't Start or Shuts Off" and "How To Troubleshoot a Pool Pump Motor - Motor Fails to Start".

User: csitg

I have a Flotec pump, I really don't know how old it is but while walking by it yesterday I heard a "POP" then the pump stopped working. Any suggestions? Thank you.

User: 

I have a 1hp Hayward Super Pump. All summer it's been working beautifully. Yesterday it stopped working. We had alot of rain,so I'm guessing that bhad something to do with it. In 20+ years it never happened before. I checked all the breakers etc. I was hoping to find a re-set button. Had no success. Any Ideas?

User: Inyopools

Raj - The winding in your low speed circuit may be bad. You may have to replace the motor. Check first that your wire connections to the pump terminal are tight.

User: Raj

I have an AO smith K48L2A1 motor in my spa.

The pump will not start at low speed, it simply hums and then stops. The pump will start at high speed and will run at low speed once it has been started (no load).

I had both the start and run capacitor tested, and they passed. But to be sure, I replaced the start capacitor anyway (original 124-149) (replacement 130-156MFD). But this still hasn't resolved anything, and the pump will hum and not start at the low speed.

Any ideas what to try next?
Thanks
Raj

User: Inyopools

scott44 - This sounds like a voltage issue. Starting then shutting down after a few seconds is characteristic of having 115V supply voltage going into a pump that is configured for 220V. Also check that the wiring to your motor is not damaged and that you have tight connections to the motor terminal.

User: scott44

My AO Smith 1 1/2 hp 3600 rpm motor starts, but makes an odd noise and is clearly not going 3600 rpm, more like 500 rpm. Then shuts off after a few seconds of this. Could this be a capacitor problem?

User: Jpstone13

So installed a matching capacitor in mfd and hz yesterday although it was a different brand. I know it is important to hook it up properly but when I took the new one out it had side posts as opposed to vertical when in a similar position. I installed it and turned the pump on and tho it did start, if made a high pitched noise and then a pop followed by a spark that tripped the circuit and shut off. Two questions. One, did this happen because I hooked it up incorrectly or could it be that the motor was already bad? Two, did I just ruin my motor by doing this?

User: Inyopools

JamesTheTruth - The start capacitor is generally in the back of the motor under the cover. I would assume that you replaced that capacitor already. Some motors also have a run capacitor on top of the motor under the hump. Your motor does not have a hump, so only one capacitor. If your motor is still humming, I would guess it's has a damaged windings coil and will need to be replaced.

User: JamesTheTruth

I have successfully replaced the capacitor but pump but pump still Humes then freezes. Dealer said there probably is a starter capacitor also which needs replacing. Where is the starter capacitor located on a A.O. Smith UST 1102 1HP 3450.

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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.