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

WRITTEN BY: 

  3.17 out of 5 stars on 18 ratings
(Click on a star to add your rating)

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

Top

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, you problem may be bad motor bearings. Replace bearings/motor or impeller as required.

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 motor 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.

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.

Comments

Top
(161 to 176 of 176)

InyoPools Product Specialist  Posted: 1/25/2015 

Chris - Sometimes when a motor sits and hums with the power on, a section of the windings short out, leading to higher current and hot motors. Have the windings on your motor checked. If bad, you will probably need a new motor. With minor exception, all motors, including yours, spin CCW when looking at the pump end. Also, a pump motor will only spin in one direction. It cannot be reversed.
 Reply

InyoPools Product Specialist  Posted: 1/25/2015 

Chris - Sometimes when a motor sits and hums with the power on, a section of the windings short out, leading to higher current and hot motors. Have the windings on your motor checked. If bad, you will probably need a new motor. With minor exception, all motors, including yours, spin CCW when looking at the pump end. Also, a pump motor will only spin in one direction. It cannot be reversed.
 Reply

 Posted: 1/21/2015 

INYO: My Hayward TriStar SP3207x10 pump won't start, only hums. Unit is 5.5 years old. Impeller spins freely using screwdriver through water intake. I was able to start manually by spinning the shaft at rear of motor. I assumed a bad capacitor, but after a few minutes, pump turned off. Pump housing is very hot to the touch. I manually started 2 or 3 times over 2 days (~6 times total), and each time it quit. There are no odd noises or other noticeable issues.

Would really appreciate your input on possibilities? Can you tell me which direction the impeller spins on this specific pump (I spun only clockwise)? Would an impeller spinning in reverse cause overheating?

Thanks for your time and expertise!

 Reply

InyoPools Product Specialist  Posted: 9/29/2014 

Tristar Pump - If your pump is squealing and shuts off right away, the bearings are probably going. Most people buy a replacement motor at this point. If you want to try to replace the bearings, see our guide on "How To Replace the Bearings in a Pool Pump Motor - Part I". This requires special equipment and some patients. If you want to replace the motor see our guide on "How To Replace the Motor on Your Pool Pump".
 Reply

Anonymous  Posted: 9/27/2014 

I have a Hayward Tristar pump, about 5-6 years old. Now, when it starts, either by the auto timer or manual switch, it runs for about 5 seconds then turns off. When the auto timer is on, the pump keeps turning itself on, but turns off after about 5 seconds, about every 10 minutes or so. The pump is hot to the touch, even though it is not running. When it comes on, it makes almost a high-pitched squealing noise. Any suggestions?
 Reply

InyoPools Product Specialist  Posted: 7/24/2014 

pmorris - The start capacitor is usually underneath the back cover where the power goes into the pump. Some more basic pumps do not have them. From your description, however, I doubt you have a capacitor problem. If the motor starts but runs slowly, it sounds like you have a bearings or windings problem. Usually when a motor gets to that point, people replace then.
 Reply

 Posted: 7/22/2014 

I have a A.O Smith 1/2 HP pool pump motor in a Leslies Hydramax II pump
(K48J2N105) It was humming and tripping the breakers so I removed the motor and it labors and turns very slowly when powered.. Where could I find the capacitor for this machine. Is it obsolete?

 Reply

InyoPools Product Specialist  Posted: 7/21/2014 

Mathew - Your new capacitor is probably all right. You can replace them with a slightly larger capacitor. And if your motor is acting the same, I would suspect that your problem is not your capacitor. Sometimes the motor windings get a hot spot in them and can get hung up in that area. Have someone check the continuity in the winding to see if that's your problem.
 Reply

 Posted: 7/21/2014 

I have a boat lift motor that starts and runs fine in one direction, but just hums when trying to start in the other direction (the rotation that lifts the boat.) If I spin the drive pulley in the "up" direction, though, the motor takes right off and lifts the boat with no obvious problem. So, I suspected the start capacitor was bad.

This is a "AO SMith" 3/4HP electric motor. The old "Mallory" capacitor on the motor is labeled:
565-678MFD 110VAC
610807-15 60HZ
235-9811-04


The local electric supply shop didn't have an exact match, so I purchased a DiversiTech capacitor with this rating: 590-708UF

After installing it, though, the behavior is the same. Unless/until I spin the shaft, the motor just hums when switched to go in one direction (even under no load) but runs fine in the other direction.

Do you think the DiversiTech capacitor is the wrong size? If not the start capacitor, what else might be the problem?

 Reply

InyoPools Product Specialist  Posted: 10/29/2013 

Rich87 - With the power (and timer) switched on, Put the leads of a multimeter across L1 and L2 and make sure it reads 230V or so. Also check that the connections to L1 and L2 are tight. If no success, you may have a bad pump. I would then call Pentair.
 Reply

 Posted: 10/28/2013 

I just installed a brand new WhisperFlo 3/4 pump. I attached red/green wires to L1/L2 and green to ground and attached the earth cable to the housing. I have good 120V coming off the timer to both red/green..switch on motor is switched to 230V (good 120V to Red 120 V to green). The shaft turns easily yet it does not work. Nothing happens when I turn the power on. I reversed the L1 and L2 (Red/Green) shouldn't matter anyway...nothing happens. Think I just got a bad pump froim Pentair?? Anything else I can try?
 Reply

Anonymous  Posted: 10/2/2013 

I just replaced my whisperflow dual speed motor and it initially started on low speed, then I engaged the high speed timer and it stopped and just hummed at me. I wired it up just like the old motor so I am missing why I am having an issue. I have rear motor access and it moves freely when there is no power applied but once I apply power the shaft is so hard to turn with a wrench. I know it has got to be something simple. Anyone out there that can help?

Charles

 Reply

InyoPools Product Specialist  Posted: 7/4/2013 

klmathews - Our data base shows your sp-1610-z1 as a 1.5HP motor with a Service Factor (SF) of 1.25. That's a real or total HP of 1.88. Your motor is probably too big for your 1 1/2" pipes and may be working hard to push a greater volume of water through the smaller pipes. Also for that size motor you need 10ga wire for lengths under 50'.
 Reply

 Posted: 7/3/2013 

I recently replaced the pump on my above ground pool with a used 1 hp hayward sp-1610-z1. When I first fired up the pump it ran fine for awhile, then started fluctuating, and eventually heated up and stopped. After much research I determined that the pump was originally wired for 240v and I reset it to 120v. The pump ran steady and smoothly but overheated in less then 30 min. My wiring is 12ga throughout. I checked the voltage at the input and output of the timer and at the motor terminals L1/L2, all measured 120v. I believe all the wiring is good. How can I diagnose other electrical and mechanical issues? I don't hear any bearing squeal but the pump is relatively loud. I'm using 1.5" PVC in and out and the water flow out of the return seem reasonable (i.e. not running down the side of teh pool and not shooting across the pool.
 Reply

InyoPools Product Specialist  Posted: 6/10/2013 

petergw1 - Sometimes the timer mechanism goes bad and you might want to check that first. If you are comfortable using a multimeter, turn the timer on and place the meter probes on the timer output terminals - #2 and #4 on a standard Intermatic Timer. See Step 8 is our How To Guide on "Installing a Salt Chlorine Generator". This step shows you where the wires to the pump are. Should read about 240V assuming your pump is configured for 240V. If that works, take the electrical cover off the motor, and put the meter's probes on L1 and L2. If the motor is getting power, this will read 240V also. Be careful with these measurements. You are working with 240V. See "How to Wire a Pool Pump" for more detailed instructions.
 Reply

 Posted: 6/10/2013 

This web site has great easy to read diagnostics for pool eqiptment services,THANK YOU! I have a question: My pool equiptment has been working great, aside from cloggs from debris,but 1 day My 3x year old 2HP pool motor wont start? The impeller is spinning freely, I checked the starter capaciter with a multi meter & it seems to be working ok & even changed it with another of the same, Fuse panel is ok, the pool timer appears to be working, but when I flip the pool timer switch to "on", a "electric "click sound comes from where I think is the pool heater,& the pool motor does nothing,& doesnt even try to start? Im not sure how to check to see if the motor is receiving power though? The motor was replaced a few years ago, and has not given any signs of wearing out? Please help me, im going crazy with this? Thx, Peter
 Reply