Bosch Classix 6 1200 Express - leaping about the kitchen

[JohannD]

This machine is abt 4yrs old, and recently has taken to bursts of full motor speed in the wash cycle, which with the water in, makes the belt squeal & the machine jump about! It's about 1 sec full-power then a 30 sec pause to recover. In the past it'd do this a few times (always anticlock rotation) then settle down to the normal anticlock/clock slow drum rotation and finish the complete wash/rinse/spin cycles successfully, but occasionally with a burst in the rinse cycles. Have had to reset F:21 errors in the past, when it went on too long.

Now it does it almost from 1st rotation, and never recovers, ending up with another F21 error. Occasionally in the past it went mad mid-cycle, F21'd and had to be reset. I did get it to run ok for a while after an F21 reset today, but it went bonkers again mid-wash and eventually F21'd again. After a reset I was able to do a spin cycle, with full motor speed control throughout the spin cycle.

I've tried running it full, nearly empty, re-distributed the load mid-wash, diferent programmes & it still misbehaves. It's sitting level too.

I've already had the motor apart a couple of times - windings look fine, no overheating, checked the brushes (ok) and all the blade interconnections between it's sections. I've checked the tacho continuity (ok) and also scoped the tacho signal on the control board, it's there & a nice & smooth sinewave. As far as I can see the motor looks fine - there's not a lot to it to be honest! The control boards look ok too as far as I can tell - no bad solder joints etc.

I was wondering if there's some sort of "unbalanced washing" sensing going on & by whizzing up the washing tries to even it out, but it seems a bit drastic!

Sorry for the wordy description, just wanted the whole story available! Any suggestions gratefully received - when it behaves it works fine so I'd rather not skip it & buy new if I really don't have to.

Thanks.

 

[JohannD]

For what it's worth and anyone with a similar problem, I fixed the thing!

Turned out to be an intermittent connection between the tacho coil & the interconnection plate in the motor - the one with the rectangular socket that the cables plug into. When I checked the signal the first time I must have been lucky (or not, in a way).

I rechecked the signal & it was there sometimes, other times not or very ragged. Poking the scope probe on the gold interconnection blades I could restore the signal.

Fixed by hoiking out the female socket connectors on the tacho assembly, repositioning the copper wires from the pickup coil and then pressing the metal connector back into the plastic block. This remade the connection to the copper wires, and tightened the contact with the gold blades.

If it does it again I'd be tempted to hot-wire connections from the tacho coil to the main connector block directly - or buy a new motor!