BOSCH WFK2801 trips RCD

[OldBob]

My 21 year old BOSCH WFK2801 suddenly stopped and tripped the RCD which takes out the entire house. I reset the trip and the same thing happened. I checked the plug which was OK and tried a different socket in a different room by using an extension cable. No change. The RCD only trips when the motor starts to turn, not when the machine is first turned on or a programme selection made. This made me think it was a faulty motor or the starter capacitor.

I removed the motor and was surprised there was no capacitor evident, though reading the FAQ’s here that would seem normal, checked the brushes which were fine and cleaned up as best I could the carbon dust around the motor area. I tested with my meter and found no obvious shorts to earth. I reassembled the motor into the machine and put it on a wash cycle and it worked fine. The next wash cycle, and every test since however tripped the RCD as soon as the motor began to turn.

I reset the RCD and put the machine on to a PUMP OUT only and this worked fine, no tripping of the RCD. This reinforced my thoughts it could be the motor with an intermittent fault. However I also wondered about the capacitors in the suppressor/filter but wonder if they would trip all the time if faulty or are they load dependant? The item is not cheap to replace just “to see” what happens! Likewise, even a second hand motor is not cheap, with delivery, and is an unknown quantity.

Am I just throwing good money after bad? Any help and advice gratefully received.

[electrofix]

sometimes shorts to earth cant be found with a multi meter as its only using a 9v battery
if it has a problem its normally the armature. check it again on at least a 2 meg ohm scale

Dave

[OldBob]

Thank you for your suggestion Dave.

I have removed the motor again today and checked each of the commutator segments on 20M range and there appears to be no leakage to earth. Similarly I checked the field coils and found similarly. In view of this I removed the brushes which looked fine but gave them a good clean up, lots of carbon around the housings. While the brushes were out I wrapped a strip of 600 emery paper around the commutator and spun the motor until the brass segments were clean and reasonably polished. I carefully cut between the segments to remove any carbon deposits and finished off by giving it a really good clean with specialist contact cleaner and a small stiff bristled brush.

I replaced the motor and tried it on a spin cycle and it ran fine without tripping the RCD. Hopefully on Wednesday I can reinstall the machine and try a wash cycle. Here’s hoping! Thanks again.

Bob

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