Bosch WFT2800GB /13 no fast spin after brush change

[DaveO44]

The w/m stopped working with completely worn out brushes. Motor head end was an old one with crimped in brushes, so I purchased replacement head end. Fitted it and motor ran fine except that it will not do any fast spins. It appears to try and after many attempts stops. Suspected vibration sensor and I modified brushes to fit in the old head end. Fitted it, but with the same problem. Have checked continuity of all plug/socket ends of cable that links motor to control unit, all ok and pass a wiggle test. No service manual available, but capable of fault finding should there be one. Glad of any suggestions.
Thanks in advance.

[Martin]

Re: Bosch WFT2800GB /13 no fast spin after brush change

Did you make sure you fitted the stator in the correct way around?
What was the part number of the new brush end housing? (It should be 00496876)
Finally, if the commutator segments in places are an uneven colour chances are the armature is knackered and only a new motor will cure. I suspect the latter TBH. 🙁

[DaveO44]

Re: Bosch WFT2800GB /13 no fast spin after brush change

Thanks Martin.
There is an outside chance that the stator was connected the wrong way around to the main body of the motor. I am very methodical when disassembling, but did not mark the parts beforehand, however I compared against a photo of the same motor offered as a spare and my reassembly checked out with the photo.
I have been reluctant to reverse the stator end in case that would damage the motor or control circuitry.
The invoice from Uk Whitegoods shows the part number to be 496876.
There was no complaint about high speed spinning before the motor gave up the ghost and failed to spin at all. Also both stators with the new brushes present the same problem e.g. working fine at all normal speeds, but failing to get the correct revs during the spin cycles, though trying.
I must admit I have a reluctance to purchase a new motor and then find the fault is part of the control unit. By that time it might have been worth replacing the whole washing machine instead.
Would the motor work at all if the stator was reversed?
Tks

[Martin]

Bosch WFT2800GB /13 no fast spin after brush change

DaveO44 wrote:Would the motor work at all if the stator was reversed?
Tks

I’m not quite sure, though it is quite possible I would think. It gets the high spin speed through an extra field coil tapping. So it’s either fitted the wrong way round, or the motor plug lead for that circuit has broken, or the module on the base has thrown a wobbly.

Is the armature commutator nice and clean with no raised or discoloured copper segments? (Very important to double check)

[Andy jones]

Re: Bosch WFT2800GB /13 no fast spin after brush change

Just checking the obvious but are you trying it empty

[DaveO44]

Re: Bosch WFT2800GB /13 no fast spin after brush change

Thanks Martin and Andy,
The w/m is being used at the moment when we have lot of washing, which is then transferred to our spare machine for a spin, then back for a dry if necessary, so it has been tried empty and with normal loads.
I have some fine emery paper and switch cleaner, so will give the commutator a spin with some paper around it to clean it up and then clear out the segment gaps if not designed to be flush. I will also see if I can spot any open circuits on the field and armature windings, keeping in mind that there might be a reversal with the connections. Perhaps I can deduce if a reversal is in fact the cause.
Cheers David

[DaveO44]

Re: Bosch WFT2800GB /13 no fast spin after brush change

Martin,
I have now fixed the motor – your information that there was a separate winding for the fast spin led me in the right direction.

In fact the stator was installed the wrong way around, but by inspection and checking with the multimeter, I was able to reassure myself that there was unlikely to have been any damage.

With the stator the wrong way around there was no field winding resistance to see between pins 1 and 2 and the only field winding resistance came up as 1.2 ohms between pins 2 and 3.
With the stator the correct way, between pins 1 and 2 there is 1.6 ohms and between pins 2 and 3 it is 3 ohms.
The armature is connected between pins 4 and 5 and gives around 3 ohms either way, while there is apparently a semi conductor device between pins 6 and 7. I was told that the vibration sensor is within the motor by an ex Bosch technician, so it might be that.

Many thanks for your help – hope my result will aid some other unfortunate who forgets to mark the pieces before dismantling. I guess the photo I saw on the web, indicates that the construction of these motors is not robotised and the laminated iron core section can be selected either way around for fitting with the field coils.
Cheers David

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