There are two completely different symptoms that many people confusingly report using the same language so it’s important to make sure you are looking at the right article. If when you say the washer is not spinning you mean (as many do) that the drum is not revolving on any part of the cycle then you need a different article – washing machine drum not turning. If you are investigating a washer where the drum is turning normally on wash and rinses but it’s just not doing the fast spin at the end of the cycle then continue with this article.
Not spinning at the end of cycle
The first thing to check is the wash load. Modern washing machines have built in out of balance protection and will refuse to spin out of balanced loads to protect against serious damage. The worst loads for this problem are single items which are heavy when wet, or small loads, particularly if they have a single heavy item amongst them.
Therefore there is always a possibility there isn’t an actual fault. A quick check would be to see if the washer spins with no load in, or with a totally different (fuller more balanced) load. If it does, check this article carefully to understand this problem – Washing machine wont spin just one item or very small loads
Not spinning because it can’t drain the water properly
Is it pumping out the water properly?
A washing machine will also refuse to do a fast spin if it isn't draining the water, either at all, or just not fully within the set time allowed due to a partial obstruction. However, don't start suspecting a pump problem unless it's obvious that the washing machine isn't draining the water out properly and leaving quite a lot inside. Don’t mix up the amount of water that will naturally be left inside because the washer hasn’t spun with the amount caused by not having pumped it out properly.
If you suspect a pumping out fault follow this article – Washing machine won't empty water
Not spinning due to pressure system fault
Maybe it just thinks it isn’t draining water because it’s not getting the “water has now gone” signal.
The washing machine knows water has been successfully pumped away when the pressure system tells it. A faulty pressure switch or (more commonly) a blockage, can stop the signal being sent, so the washer refuses to spin. It will often do the slow turning at the beginning where it distributes the laundry, then just click and stop.
To understand how a washing machine controls water levels and knows when the water has drained away see this article – How washing machines control water levels (there are links in the article to common pressure system faults and DIY repair help).
Not spinning because motor is faulty or belt slipping
It is possible for a worn motor (or more commonly worn carbon brushes) to cause it to struggle to get up to spin speed but manage to turn the drum on wash and rinse. Normally such a fault would also cause problems on wash and rinse so it’s not too likely. However, if when it gets to the spin cycle the motor appears to attempt a spin but makes a strange grating or crackling noise and sounds half hearted (maybe fluctuates up and down in speed) there could be a fault on the motor. If the motor is sparking a lot you can suspect the brushes but if it is not sparking excessively it could be an issue on the PCB or a connection fault – get an engineer in. The most common issue with motors is worn carbon brushes (How do I know if I need to fit new carbon brushes?).
If a drive belt is worn it could be slipping. It’s not so common these days but should be easily observed with the back panel off if this is what is happening.
If the water is being pumped out OK, and it doesn't appear to be an out of balanced load, then proper fault finding is necessary, which really needs the use of a continuity test meter and proper knowledge of washing machine repairs. If it isn’t caused by any of the faults described above it only really leaves faults on the main PCB (or module), connection faults, motor faults etc. It would be unwise to start buying parts speculatively, which could easily prove an expensive mistake.
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