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The drum in my Bosch Serie 8 washing machine stopped turning recently and after a bit of internet research it sounded like the motor brushes had worn down. I bought new "official" (allegedly) brushes from a reputable website and replaced them - the old ones were definitely worn down to nothing compared to the new ones so I figured that would solve the problem.

However, having put it all back together again, the motor is only turning intermittently in short stutters, makes an electrical fizzing sound when it turns, and gives off a faint burning smell like underneath the scalectrix cars I had as a kid.

I'm pretty sure I put the brushes in the right way round and reconnected everything correctly, but there's obviously something wrong somewhere.

Other relevant info:

I can't upload a video with sound, but here's an animated gif in case it helps:

Washing machine motor stutter

  • The first time I turned it on and started a simple "rinse" cycle there was a flash inside the drum and it blew the RCD for the kitchen sockets where the washing machine is plugged in

  • I reset the RCD and tried again, and it's now doing the stuttering movement and fizzing thing

  • It happily draws water into the machine - it's just the motor / drum not turning properly

Is this possibly a problem with the new brushes, or my fitting of them? Or should I play it safe and just replace the whole machine?

Any help / pointers welcome...

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  • A flash seen could mean there was/is a short between a hot and neutral/ground. Could be cause by a wire in wrong place, take apart and check. Could have burned out a motor control/capacitor/sensor. – crip659 May 8 at 20:41
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Unplug the machine , hopefully you did not fry the motor , let it cool down! First remove the brushes, both of them and rotate the motor while looking at the armature, there should be even segments all the way around this is the commutator it should be a even chocolate brown in color. If any of the segments are missing the motor is toast.

All the segments there hopefully not two badly burned you may need to seat the brushes it sounds like the cup to the brush was not correct (common) or they were installed 90 degrees out. So only the points were touching the com.

Large motors we seat the brushes with some emery around the com, small motors I will check the fit even the highest quality brush may have a different cup or diameter com. So the brush arcs, the other thing that can happen is the brush is to tight in the holder it should slide all the way in without pressure needed or once in it should fall out if pointed down, if snug a quick pass over some emery cloth or 400+ sandpaper will quickly reduce the size.

If the brush fit to the commutator is bad enough damage to the com can ruin the motor.

When you pull the brushes examine them for burns. Arc marks in the center on each side is evidence of the brush in 90 out. Burns on only 1 brush across the entire brush point to over sized not in contact.

If there are divots in the com that is a higher level of repair than you may the ability to do.

When brushed motors are running properly there should be a fine line of arcs at the edge of the brush that move or dance back and forth.

The big flash and the rcd tripping may point to a non repairable problem for DIY. But checking the com and brush seating is the first step.

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  • Thanks for the comprehensive answer. In the end I seemed to be fighting a losing battle so I ordered a new machine - didn’t want to risk causing an electrical fire through ham-fisted diy. That, and the pile of laundry from 2 kids was growing faster than I could get express delivery for a new motor for :-). I’ll dig the brushes out to see if they’ve got any of the symptoms you mentioned, and I’ll post a picture if I can get a good close-up. Thanks again. – mclayton May 9 at 6:45

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