How To Determine Why a Motor Won't Start or Shuts Off


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This guide discusses the common problems related to a motor that won't start or once it does start shuts off after 5 minutes.

Step by Step


Step 1

No power to the motor- Check for improper or loose connections, open switches or relays and blown circuit breakers or fuses. Check for broken power cords.

Step 2

Jammed motor - Check that the motor shaft rotates easily. If it's stuck, check that the impeller is not jammed with debris. Check that the impeller or diffuser is not broken. If the impeller is good, your problem may be bad motor bearings. Replace bearings/motor or impeller as required.

Click here to view motor bearings. 

Click here to view pump impellers.  

Step 3

Motor hums but will not turn over - Check for a bad capacitor. You may have two: a run capacitor and a start capacitor. Some motors have a governor at the electrical end of the shaft. Check that it is not stuck open. If your capacitor(s) and governor are good and the motor shaft rotates easily you probably have a burned out motor coil and you will need to repair or replace the motor.

Click here to view motor parts.  

Step 4

Motor gets hot and shuts down - Generally due to low voltage or being overloaded. Check that the motor is wired correctly. If the motor is configured for 230V and has 115V coming in, it will shut down after running 3-5 minutes. Check for loose connections. Check for undersized wiring. For a hook-up to the circuit box of under 50', pumps of up to 2HP wired for 230V need No. 14 size wire, For pumps wired for 115V, the wire size must be No. 14 for 1/2 and 3/4 HP; No 12 for 1 HP; and No. 10 for 1 1/2 and 2 HP. Check that the motor is not overloaded. Does the pump have the correct impeller and diffuser for this motor? Is the impeller worn and rubbing on the diffuser. 

Step 5

Note: Most pump motors have Automatic Thermal Overload Protection. The motor will automatically shut off before the motor generates enough heat to damage itself. Once a normal heat level is reached, the motor will automatically restart. CAUTION: If the motor operates in this on/off mode for any length of time it will burn out.

Click here to view replacement motors. 


(81 to 120 of 225)

 Posted: 11/1/2018 

I have a Jandy RS4 system. My filter pump won't start from the remote unit, but will start from the power panel when the unit is in service mode. Since it starts at the local button, does that rule out the relay? Should I be troubleshooting the remote unit and the board? Thanks for any help.

InyoPools Product Specialist  Posted: 11/2/2018 

Hello Matt - You are correct. It doesn't sound like a relay issue. We would recommend looking at the board and remote/receiver.

 Posted: 10/31/2018 

I have a US Motor 1081 Polaris Booster pump. It recently began to not startup when power was on. But when I spin the shaft, it starts and runs fine. It does this with the 370v, 35mf run cap connected and disconnected. I connected a 125v start cap to it and it starts up but it makes noise. It's not not the right size but would this indicate that the run cap also functions as a start cap and that it is bad?

InyoPools Product Specialist  Posted: 10/31/2018 

Hello Sklemetti- Your problem could be a defective run capacitor. You can rule out the capacitor by testing it with a multimeter. Check out our article titled "How to Test a Pool Pump Capacitor". If the capacitor checks out ok, your problem could be a phase winding. If that's the case, the motor should be replaced. The replacement motor for the Polaris Booster Pump is part number B625.

 Posted: 10/3/2018 

We left the area before the hurricane and turned off the swimming pool motor. Upon our return the motor just hums but does not engage the pump. We have checked for debris etc., Is here anyone in the Clarkton NC or Elizabethtown NC that works on swimming pool equipment. We need help! In addition to the present problem we also need new plastic pipes and other parts of our equipment although getting the pump started so we can clean the pool we will need to purchase some equipment. Kerry Baidin

 Posted: 5/8/2018 

Hello Patti - We could not find your order in our system. What motor did you order? Are you supplying 115v or 230v to the motor? Have you tested the voltage to make sure power is getting to the motor?

 Posted: 5/7/2018 

I replaced the motor and still will not start. I bought new motor last week from you. any suggestions?

 Posted: 5/2/2018 

Thanks for the reply. I was thinking it was the relay, too. I was only doubting it because everything I found online indicated that when relays fail, they get stuck shut, meaning that the pump won't shut off. I couldn't find any case where the opposite was true, but I'm guessing it's possible.

 Posted: 4/30/2018 

Hello Jeff - It sounds like the relay is the problem. You can also check the connections at the relay. Sometimes the lines will get loose and it can cause the motor to run intermittently.

 Posted: 4/29/2018 

My pump won't start unless I whack the control panel on the wall with my hand. Then it might run continuously, or might start and stop intermittently. Is there something inside the control panel that might need to be replaced. I have read online about bad relays, but not sure what to look for.

 Posted: 3/9/2018 

Found the culprit: I pulled the motor apart and found a very thin 1" ring lodged between the windings and the housing. It must have fallen off the back of the end bearing into the motor when I pulled the shaft for the bearing change. The ring wasn't listed on the drawings of the motor, nor did I see it in the motor when I put the shaft back in. I suspect that it has been moving around in the motor causing the intermittent failure. Pump started straight away once I had it all together and hooked up again.

 Posted: 1/19/2019 

Wow..perfect description of my problem. I replaced the bearings, seals and impeller with the pump running fine for couple years. It is now doing the exact same thing as yours, intermittently tripping the breaker! I will let you know if this little ring (aka.culpret) is my issue ..or will be asking if there are other potential remedies. Thank you.

 Posted: 3/8/2018 

My 3 year old 1hp Certikin pump was running without any issues until the bearing failed. I replaced the bearings and the water seal myself and the pump was turning smoothly. Now when switching the pump on, sometimes the breaker trips immediately, sometimes the pump runs for 5 to 10 seconds before the breaker trips while other times it just runs fine and does so for many days switching on and off on the timer until the breaker trips again. Once the breaker has tripped I need to reset it sometimes once, sometimes more times for the pump to start but when it finally runs, it keeps running fine, it doesn't trip. This morning after cleaning the pool, switching the pump on/off various times, the pump now keeps tripping the breaker. I live in a warm and dry climate, the pump is dry hence moisture is not likely to be a possible cause. Any suggestion what may cause this is much appreciated. Thanks.

 Posted: 11/9/2017 

I came home last week to a no flow light on my panel. Checked the pump and it hummed, but didn't start - and was getting 230V across L1/L2. Odd thing was that the heater started to fire up while the pump was humming, even though the heater was set to off. As the pump was 12 years old and a little noisy, I decided to order a replacement Century SN1202 from Inyo (and a new impeller and gasket kit). I installed all the new stuff today and had the exact same problem when I was done...pump hums and the heater kicks on. As before, I'm getting 230V across L1/L2. Any ideas before I call the pool dude? thx

 Posted: 10/31/2017 

Hello. When I turn on my booster pump while the filter pump is running the filter pump shuts off. This causes no flow to go to my heater so I get this boiling sound in side the heater. The system was installed in May. It is a Jandy variable speed pump and 1.5 horsepower booster pump. This problem just started maybe a month ago. Thanks.

 Posted: 9/13/2017 


funny thing. Exact same thing happened to me. I also did the exact same test as you measure the voltage from ground to L1 and ground to L2, both were reading 110V AC. I did NOT however, check it with another power cord. Have you figured out what's wrong?



InyoPools Product Specialist  Posted: 7/21/2017 

Maxair - I would bet that the low side of the switch has failed. Try replacing the switch.

 Posted: 7/19/2017 

hi-flo ph2200-6 1 yr old only turns on HI. the Low setting wont work.

InyoPools Product Specialist  Posted: 7/9/2017 

Kevin - I would have been surprised if both of your motors failed at the same time, so I would have questioned the circuitry to the motors? If you said you measured 120V on both the L1 and the L2 leads against a ground, you should have 230V across L1 and L2 which means your supply voltage is 220V. Are your motors configured for 220V? When you said you plugged an extension cord into an outlet, was that an 115V outlet. Are your old motors set up for 115V?

 Posted: 7/7/2017 

Hello, my two pool motors (1HP and 0.75 HP) have suddenly both stopped working (no humming, completely dead). Naturally I assumed the motors were broken as they looked very old. So I bought two replacement motors from here, hooked both up the same way the old ones were and still absolutely dead. I checked the Voltage on both motors (GND to L1, and GND to L2) both read 120V. So what on earth can be the problem? Side note (don't try this, danger): To make sure that the issue isn't the motors, I took an old extension cord and cut it to expose the 3 wires, plugged it into an outlet and held the wires to the OLD motor, and surprise it started running. Thus the old motors were probably not broken and something must be wrong elsewhere. ANY IDEAS??

InyoPools Product Specialist  Posted: 7/1/2017 

Bnd31 - The motor humming is a symptom of a bad start capacitor. So I would replace that first. Usually, the start capacitor is in the back of the motor and the run capacitor is on the top. I'm not sure why the motor stops after a few minutes. It sounds like your thermal overload protector is cutting the motor off because the motor is too hot or the thermal overload protector has gone bad. Otherwise, your motor may be going bad. Try replacing the run capacitor if your motor has one. See our guide on “How To Replace AO Smith Motor Parts – Overview” for motor parts information.

InyoPools Product Specialist  Posted: 6/30/2017 

Anonymous (pump won't start) - I see no correlation between backwashing the excess water from your pool, and your pump subsequently not turning on. If it's humming, it may need a new start capacitor. Note: if your MPV has a Waste option, you should use that setting instead of Backwash to drain off your pool but that should have no impact on your motor not starting.

 Posted: 6/30/2017 

When I turn the pump on, It just hums but dont start. Im able to start it by turning the shaft and turning the pump on at the same time. But it shuts off by itself in few mins. Then it wont hum at all if i try to start right away. If i let it sit for a while, i hear the click, then i turn the pump on, hums, turn the shaft and starts.. dies again in a while..

Any help?? I havent checked the capacitor yet, looks like theres one at the top of the pump. And abt the wiring issues, low and hight voltage issues, i have never altered anything at all. We moved in last year and the pump has been working fine so far


Anonymous  Posted: 6/29/2017 

I stupidly forgot to turn the garden hose off, filling my pool with water for 9-10hrs, I backwashed all the excess water and it's back at its regular level, however, the pump won't turn on.
What do I do? It was working fine earlier


InyoPools Product Specialist  Posted: 6/14/2017 

Anonymous (dead motor) - Make sure that your motor is configured to match your supply voltage. If you have 220V coming into the motor, the motor should be set up to receive 220V. Recheck your wiring. If the motor still doesn't work, talk to the dealer again. Have him check the motor.

Anonymous  Posted: 6/13/2017 

Hello. I just replaced the motor on my pool pump. The old one was only two weeks old. The old one just stopped working. Took and exchanged the motor for another one. Hooked it back up, and nothing. Replaced breaker and timer. Still nothing. I know power is making it to the timer and motor. The motor is a century USQ1152. Not sure where to go from here. Thanks for any help. Bobby

InyoPools Product Specialist  Posted: 6/12/2017 

Gary - You may be in an area with unstable supply voltage. Some motor reps have suggested switching to a run capacitor with the next level voltage. If you have 370V now, go up one level in voltage to 440V.

InyoPools Product Specialist  Posted: 6/11/2017 

Ozzie - If you have a multimeter, check the voltage at the motor terminals L1 and L2 to see if your motor is getting power. If your motor has one or two capacitors, change them. Otherwise, your motor winding may have shorted out and you may need a new motor.

 Posted: 6/11/2017 

Hi there. Recently had to replace the run capacitor, Have used the same specs as the old one. New problem though, Motor starts fine but only runs for about 4 minutes and then stops for about 5 minutes, the whole process repeats. The control panel has 3 lights flashing when it stops and clears when motor starts up again. This problem is doiong my head in. Please Help.

 Posted: 6/9/2017 

Hi, I'm hoping someone can help. My pool pump is not turning on or making any noise. The intermatic timer is working as it is receiving power and I can see the gears moving through the visual motor check window. When I turn the intermatic timer on manual nothing happens. No humming noise or anything else, just nothing. What could this be? It was just working fine a couple of days ago. Thanks.

InyoPools Product Specialist  Posted: 6/8/2017 

Vacekt - Check to make sure there isn't another capacitor under the back cap. If none, and you've replaced the top capacitor, you may have a short in the motor windings. Have a pool store verify this. You may need a new motor.

 Posted: 6/6/2017 

Century Centurion motor was humming but woudnt run. I checked for debris in impeller but it was clear. I tried it multiple time but just hummed. THEN IT STOPPED noise at all. I went ahead and changed the run capacitor. Didn't fix problem. Still doesn't run or even him.


InyoPools Product Specialist  Posted: 6/4/2017 

Tubbs - Sorry, I don't understand your electrical circuit. Where is the pigtail connecting to?

 Posted: 6/3/2017 

When replacing my motor I have power going to the motor but as soon. As I plug the pigtail in I lose complete power to the motor.

 Posted: 5/26/2017 

My USQ1152 was running fine. I shut off the breaker to replace the ignitor/flame sensor on my heater and when I turned the breaker back on the pump wont run. I have power to the timer and out to the motor. Any suggestions?

InyoPools Product Specialist  Posted: 5/22/2017 

rick - I assume with a new motor that the shaft turns freely before it was joined to the pump housing. It may be that the shaft seal wasn't seated correctly and is binding on the shaft. If you take the motor out of the housing, does the impeller spin freely, If not, reinstall the shaft seal. Make sure you have the right shaft seal - GOKIT32. Is the impeller too big for the pump? See if there are any wear marks inside the pump housing.

 Posted: 5/19/2017 

first i replaced capacitor,didn't work.then i took motor to reapir shop,they suggested i buy a new one-repalced Pentair w-24 with new one ,does the same thing and the shaft will not turn?

InyoPools Product Specialist  Posted: 5/2/2017 

chad - The windings on you motor may have shorted out. I would contact the place you bought the motor and see if the motor can be replaced. It should still be under warranty.

 Posted: 4/30/2017 

Pool motor sometimes starts on a timer. But if have to power motor off for maintenance for a few minutes (to clean filter, etc), it buzzes and will not restart. I changed the capacitor with new. Same thing. The motor will hum then a click sounds. After 5-7 minutes the motor clicks again and tries to restart. If the motor does not start up after about 5 seconds the breaker trips. I also replace my breaker with new. The motor is only 6 months old and worked fine for 5 months.Where do I go from here?

InyoPools Product Specialist  Posted: 3/3/2017 

pump won't start - try shutting the motor off at with a switch between the breaker and the pump, reset the breaker and turn the pump on at the switch. Check that the breaker is good.