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Diagnose electric motor faults with our troubleshooting guide

A sudden electric motor failure can have serious consequences, whether it’s powering a conveyor, pump, fan or other application. Being able to quickly diagnose a motor fault means you can get your process running in the quickest possible time and minimise losses. Here’s how to troubleshoot seven common electric motor fault symptoms:

Motor fails to start after installation

First check that the motor has been wired up correctly – this is the most common cause of a failure to start and should be easily rectified. A mechanical fault is another possibility – it may be that the rotor is in contact with the stator or that the bearings have seized. These issues might be solved with realignment or lubrication unless there’s damage to components in which case a replacement motor may be required.

Motor fails to start having previously been running

As above, check for electrical faults first of all. Examine the fuse and circuit breaker and check that wiring has not come loose through vibration. If these seem to be fine, then check for rotor or stator damage and make sure that the load has not jammed.

Motor starts but cuts out

This can occur when voltage drops – possibly due to an inadequate or damaged supply cable. If it’s a mains power issue then other equipment should exhibit the same fault. Otherwise, it may be that the load has increased excessively – such as an overloaded conveyor.

Motor is noisy when starting

A ‘rough’-sounding motor – especially during start up – can be caused by poor shaft alignment, under-lubricated bearings or loose screws. Don’t ignore this problem – even if the motor sounds better as it settles into a rhythm. Check alignment, lubricate bearings and tighten screws where necessary.

Motor accelerates weakly

Do you have the correct-sized motor for your application? Poor acceleration often points to an undersized motor, so check with your supplier that you’ve got the right equipment for the job. A tightening bearing could be restricting rotor movement, in which case lubrication and alignment should be checked.

Motor vibrates

Ascertain whether the vibration is mechanical or electrical – a humming noise tends to signify the latter. If the fault is mechanical, then the rotor may be misshapen due to a load imbalance or bearings might need to be lubricated.

Overload protector trips constantly

A defective protector is unlikely to be the cause of continual tripping – instead, it’s probably that it’s working reassuringly well. First check that the load isn’t excessive and there are no problems in the drive line. Trips are also caused by overheating, so next ensure the motor is in a well-ventilated area and that the fan is working properly. Check for defective windings and wiring too. If all else fails and it does turn out to be the protector, then these are simple to replace.

If you’ve diagnosed your motor fault and decide it needs repairing, rewinding or replacing, Gibbons is on hand to help. Our motor rewinds and repairs division offer an emergency next-day service, with free collection and delivery within a 50-mile radius. For replacements, we have ABB motors available from stock via express next-day delivery, along with our own high-performance range. Or if you have a motor fault you can’t diagnose, speak to one of our friendly experts for advice on 01621 868138. You can also get in touch via email at


Electric Motors


  • Date: 15 February 2015 RAVI KIRAN
    I have abb drive. When I start the motor it stops after some time and it gives F001fault code and I troubleshoot all thing but I can't find that. So pls can u help me what can I do for this.
  • Date: 17 February 2015 Gibbons Group
    Hi Ravi,

    Thanks for getting in touch. Paul Scott has emailed you regarding your enquiry, but if you require any further help then please do not hesitate to contact us.

    Kind regards

    Gibbons Group

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