Bosch 1600 motor not turning

[Quinch]

I'm new here, so apologies if I've missed something. I've done some searching but could find anything that matches.

I've got a Bosch Exxcel 1600 classic (WFX3267GB/10) which won't turn the drum. I've had the back off, checked the belt and replaced the brushes (which seemed to be the obvious culprit), but no success. The machine fills, drains, and there's a relay clicking at the points I'd expect the motor to start.

The day before I noticed the problem, something tripped the breaker for the sockets the washer is on. My assumption had been that the worn down brushes had caused it to trip, but now I'm wondering if something else was the problem. A new motor is £150, and I don't want to spend that to discover there's another problem.

Is there something other than the motor that might be causing this?

 

[zipper]

It blew a fuse...or your rcd?
Does the door lock?

 

[Quinch]

The RCD for the sockets blew. After resetting, the machine now does all the things I would expect it to do. The lights come one, the door locks, the drum fills and empties, the motor just doesn't turn.

 

[Quinch]

In the hopes that it might help, I've finally replaced the trusty multimeter.

There's an 8 pin block on the motor. There's continuity between 1-2, 1-3, 2-3 and 6-7; 6-7 is 24Ω, and the other 3 are 1-2Ω

There's also continuity between 5 and the brushes. The brushes show 5Ω between them, varying when the motor is turned by hand. There is also continuity between the brushes and the commutator.

 

[zipper]

So what convinces you the motor is faulty?
If your rcd tripped it indicates an earth fault (not necessarily on the motor). An rcd trip can be caused by an earth fault on any of the electrical components, including the wiring. If your pcb blows this can also potentially knock out your rcd. Bosch motors normally have 3 pins from the field windings (with continuity between all three), 2 pins from the armature (with continuity), & 2 pins from the tacho (23 ohms). The eighth pin is not used (check the motor plug to verify that there are only 7 cables into the motor feed plug). I don't have the manufacturers values to hand. There is a motor overload in the armature circuit, if this had popped there wouldn't be reading continuity in the armature circuit. Unless you have (or had) an earth fault on the motor the chances are that the problem lies elsewhere. Really you ought to check all the components with a 500v megger to find the source of the rcd trip. But all you can do with a multimeter is put it on the highest scale & hope for the best. Check for a bad reading to earth as best you can with your multimeter. Then inspect the pcb for damage.

 

[Quinch]

So what convinces you the motor is faulty?

Other than it not turning, and everything else seems to be doing the right kind of thing. If I was convinced I wouldn't be asking for help

Bosch motors normally have 3 pins from the field windings (with continuity between all three)

Looks like that's pins 1-3.

2 pins from the armature (with continuity)

Not found a pair doing that - would expect that to be 4-5

2 pins from the tacho (23 ohms).

That would appear to be 6-7.

There is a motor overload in the armature circuit, if this had popped there wouldn't be reading continuity in the armature circuit.

Which there doesn't appear to be, assuming that to be 4-5, which would fit with the other pins.

But all you can do with a multimeter is put it on the highest scale & hope for the best. Check for a bad reading to earth as best you can with your multimeter. Then inspect the pcb for damage.

What am I checking to earth? The pin block, or something else? Sorry to be slightly dense.

Thanks for your help.

 

[zipper]

Most Bosch motors have a small silver object located on the brush assembly in the motor endshield. It is about the size of a postage stamp & has two connections. This is the overload device & it is connected in series with armature circuit. Check if it is O/C. If this blows you won't read continuity on pins 4 & 5. Obviously this means dismantling the motor. The bad news is that you can't buy the overload stand-alone from Bosch (only the complete motor). There is a workaround but it is a very fiddly affair (that's providing there isn't a fault on the motor windings that caused it to blow in the first place). I would still check the pcb for obvious damage because if the reversing relay has failed it normally takes out the overload. A m.meter isn't the right instrument to use for finding earth faults because it only puts out a couple of volts. But if that is what you have to hand all you can do is set it on the highest resistance scale. Put one lead to earth & the other on the motor pins, look for a difference in readings. The same applies with other components.

 

[Quinch]

Awesome! The overload device is showing no continuity, so looks like that's the bit that's gone. I'll give the PCB a once over, but that would certainly explain why the motor isn't turn.

Thanks for your help.