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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InyoPools Product Specialist  Posted: 5/14/2014 

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.

 Posted: 5/14/2014 

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?

 Posted: 5/6/2014 

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?

InyoPools Product Specialist  Posted: 5/2/2014 

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.

 Posted: 5/1/2014 

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.

InyoPools Product Specialist  Posted: 4/14/2014 

txtngauge - Assuming you protected the motor from freezing (if applicable), it should work now. Use a multimeter and check the electrical circuit to your pump to make sure you are getting power to the pump. Check the wiring under the motor cover to make sure the contacts are tight.

 Posted: 4/13/2014 

Just tried to start up our pump and NOTHING...the pool is only 3 years old and we had no problem before closing the pool last fall. any suggestions or is it just time for a new motor?

InyoPools Product Specialist  Posted: 3/18/2014 

Gampopa - If the low speed failed in the pump, you would probably have failed low speed windings and they would create smoke. Your problem is probably due to a failed pneumatic switch.

 Posted: 3/17/2014 

We have a Waterway 4 hp 56 frame 2 speed pump for our hot tub that seems to only work on high speed. When we hit the pneumatic switch to go to low speed there's no sound nor flow nor vibration from the pump. Could this be a capacitor problem or something else? I want to avoid pulling the pump and heater control out again to have it serviced.

InyoPools Product Specialist  Posted: 8/10/2013 

help - Some motors for spa and jetted tubs and above ground pool applications do not use capacitors. See our guide on "How To Identify Pool Motor Types" for more information.

 Posted: 8/9/2013 

I have a AO smith flex 48 1.5 HP

I cant find the capasitor


InyoPools Product Specialist  Posted: 7/5/2013 

motor wire sparked - Components in the motor may have been shorted when the wire sparked. See our guide on "testing the motor windings resistance". If that doesn't help, take the motor to a local motor shop and have them do a more complete check.

Anonymous  Posted: 7/4/2013 

I have a Utilitech 1HP motor 230V. On the back of the shaft is a device with springs hooked to it. This device nicked one of the hot wires coming into the motor. It sparked and I turned it off and now it will not start. I fixed the problem and I have power to each wire to the motor. The motor will not start. Help

InyoPools Product Specialist  Posted: 3/10/2013 

Mark - As a final comment on our previous communications, the engineers at the manufacturers suggest upping the voltage on your 35 MFD,370 V capacitor to 440V. The voltage represents the voltage the capacitor can handle, so the 440 would be more resilient.

 Posted: 2/28/2013 

I have a Hayward Northstar Pump with a 2.0 HP USN1202 moter (AO Smith). Over the last 4 months, the motor has started failing. A friend suggested changing out the capacitor. I did this and the system starts working again. Then in about 1 month, the motor fails again. Replaced the capacitor, works fine...for about a month, then fails. Any idea on what could cause the repeated failures of the capacitor? Should I replace the motor or could the problem be elsewhere?

InyoPools Product Specialist  Posted: 1/9/2013 

Jim - I checked your question on capacitors with a motor expert at the motor manufacturers, and he stated that the capacitor replacement would not degrade the pumping capacity of the pump.

 Posted: 1/6/2013 

Could a capacitor be a cause of a weak pump? I've replaced the capacitor on my pump because it went bad but now my pump can't suck in enough water. It doesn't pull enough to use the vacuum path or the skimmer path by themselves, so when together, there's not enough suction to vacuum the pool. The small basket by the pump looks like it's pulling in air but I've checked all the seals, replaced every single gasket, used the proper "sealant" on them, etc. Could the capacitor be the problem here or is it the pool motor?

FYI, the problem and the capacitor replacement dates do not coincide, just making note of a change.


InyoPools Product Specialist  Posted: 12/3/2012 

weekend engineer - No. The startup capacitor will change up almost immediately.

 Posted: 11/30/2012 

does a new start capacitor or a discharged start capacitor (due to removal to work on the motor), have to have a charge period before the motor will start?

InyoPools Product Specialist  Posted: 11/2/2012 

rich man - According to the motor rep - Three phase motors cannot be used on single phase power as far as we are concerned, from a warranty standpoint. They require a drive that converts single phase to 3 phase.

 Posted: 10/30/2012 

how do i check if my motor is ok using a mutimeter


 Posted: 10/30/2012 

please explain to me how to connect a 3phase motor to single phase supply coz it is an old motor with no markings on the wires.
Also tell me how to connect the start capacitor


InyoPools Product Specialist  Posted: 9/23/2012 

spanishmoss - Yes the ohms test is performed with the capacitor disconnected.

Anonymous  Posted: 9/19/2012 

thanks for your clear and informative step by step guys rock......R. S. Miller Tucson,AZ.

 Posted: 9/19/2012 

I just wanted to thank you all for this very helpful and informative site.You rock thanks.....Rick

 Posted: 9/17/2012 

Good article. I'm replacing a 30mfd 370vac/b capacitor which has two terminals. Are the terminals interchangeable, or is one positive and the other negative? Also, will the ohms test work if the capacitor is not hooked up to the motor? Thanks

InyoPools Product Specialist  Posted: 9/16/2012 

Ed - If your motor shaft does not turn freely, your motor bearings are probably going. When the motor gets to this point, most people buy a new motor.

 Posted: 9/12/2012 

Seems the motor is a little difficult to turn. Pulled the motor/impeller from the housing, and tried to turn the impeller. Not too easy. Motor does not start, hums for a few seconds, then trips the breaker. Ideas?

InyoPools Product Specialist  Posted: 7/17/2012 

Delta - I would try replacing the capacitor first. If that doesn't work, call Hayward at 908-355-7995. Their technical staff should be able to help resolve your issue.

 Posted: 7/16/2012 

I have a two-speed Hayward NorthStar. When the rotary timer clicks on (which defaults to high speed initially), the motor hums for 1 second then turns off (protective measure) for two minutes. The cycle repeats itself. If I 'manually' put the low-speed pump on first, the high-speed pump will turn on without any problem. My guess is that the capacitor is bad. Would you concur?

InyoPools Product Specialist  Posted: 7/15/2012 

Alan - I would look at replacing the capacitor first. That's your easiest fix. If it's not the capacitor, you may have a problem with the motor windings which usually means a new motor.

 Posted: 7/12/2012 

My pump keeps knocking out the RCD when I try to start it.I have checked that the motor is not seized
But the capacitor does not hum so I dont know if the capacitor is gone completely and is shorting the electrics any ideas


InyoPools Product Specialist  Posted: 7/7/2012 

kenc - I would definitely check the capacitor first. If that doesn't work, you may have a bad place in your coils and would have to replace motor.

 Posted: 7/2/2012 

My Sta-Brite 1 hp motor will not start when timer comes on. It will hum until breaker goes. I click on and off until it will finally go. My friend that opens pools loosened the impeller he said it was to tight. It worked for a month and now same issue. Now I wonder if it's the capacitor can this work and not work or if it goes that's it need new one?

 Posted: 6/21/2012 

Great post, this was my pump's issue. Thanks!

InyoPools Product Specialist  Posted: 6/5/2012 

replaced capacitor - Check to make sure the specs on your new capacitor are the same as the old. Then check to see if your new capacitor is good. Sometimes they are bad off the shelf. If those are OK, you probably have a short in your windings and will need a new motor.

Anonymous  Posted: 6/4/2012 

My start cap ruptured, so replaced it. Ensured motor shaft rotates freely, but motor now makes humming noise and does not start.

InyoPools Product Specialist  Posted: 5/12/2012 

mcswell - I'll have to check why you aren't seeing the correct page but for now type "capacitor" in our search box and it will take you to start capacitors or run capacitors.

 Posted: 5/12/2012 

Where are capacitors on your site? I've gone to Pool Parts, then Pool Pump Motors (contrary to the comment a bit further up this web page, there is no "Pool Pump Motor Parts"), but it doesn't list capacitors for the Hayward Super Pump series.

InyoPools Product Specialist  Posted: 4/26/2012 

BrownRage - I just checked with Hayward and the small 1/2 HP Super Pump does not have a capacitor. All others from 3/4 HP up have a capacitor under the end cover.