After much searching on this forum and elsewhere, the seemingly common problem of Bosch washing machines failing to spin is frequently attributable to worn or sticking brushes, mine was not!
So for those who are still struggling with this, I offer this bit of info:
My machine would start the spin cycle by draining the tub then the motor would "kick" and the drum would turn a few revolutions and stop, this start/stop cycle would repeat a few times then the machine would cancel the program.
These symptoms are characteristic of a tacho sensor failure, as the programmer starts the motor and expects feedback from the tacho in order to run the motor at the desired speed if it gets no feedback it stops and tries again a few times, then the programmer eventually gives up.
Well, the tacho coil measured ok at ~24R, I then checked the AC output from it with a DVM, zip,nada, nothing!
So I disassembled the motor and found the annular ferrite ring magnet that sits inside the tacho coil in 3 pieces:
![GALLERY]](http://[GALLERY=media, 69220][/GALLERY])
The magnet is normally a press fit on the black nylon collar between the bearing and the commutator.
I decided to use some epoxy resin to put it back together.
As not many (if any?) adhesives will stick to nylon I first I drilled some 1mm key holes in the nylon collar to give the epoxy a fighting chance of hanging on.
then applied the epoxy resin around the collar followed by the three segments of the the ferrite ring magnet, put a cable tie around the whole lot and left it overnight.
![GALLERY]](http://[GALLERY=media, 69221][/GALLERY])
I cut the cable tie off and removed any excess epoxy resin, then reassembled the motor and bench tested the tacho, by pulling on some string wound around the pulley and a clean sine wave output of of 2~6 VAC was confirmed on an oscilloscope, and a DVM showed similar voltage readings.
Put the whole lot back in the machine, and so far happy days, all working fine.
So for those who are still struggling with this, I offer this bit of info:
My machine would start the spin cycle by draining the tub then the motor would "kick" and the drum would turn a few revolutions and stop, this start/stop cycle would repeat a few times then the machine would cancel the program.
These symptoms are characteristic of a tacho sensor failure, as the programmer starts the motor and expects feedback from the tacho in order to run the motor at the desired speed if it gets no feedback it stops and tries again a few times, then the programmer eventually gives up.
Well, the tacho coil measured ok at ~24R, I then checked the AC output from it with a DVM, zip,nada, nothing!
So I disassembled the motor and found the annular ferrite ring magnet that sits inside the tacho coil in 3 pieces:
The magnet is normally a press fit on the black nylon collar between the bearing and the commutator.
I decided to use some epoxy resin to put it back together.
As not many (if any?) adhesives will stick to nylon I first I drilled some 1mm key holes in the nylon collar to give the epoxy a fighting chance of hanging on.
then applied the epoxy resin around the collar followed by the three segments of the the ferrite ring magnet, put a cable tie around the whole lot and left it overnight.
I cut the cable tie off and removed any excess epoxy resin, then reassembled the motor and bench tested the tacho, by pulling on some string wound around the pulley and a clean sine wave output of of 2~6 VAC was confirmed on an oscilloscope, and a DVM showed similar voltage readings.
Put the whole lot back in the machine, and so far happy days, all working fine.
