Bosch WFF2000GB/12 Tripping mains

[cjapeterborough]

Hi

I have been trying to fix a WFF2000 which had a faulty element.
The machine would previously wash,drain and rinse etc but would abort
all wash programs before rinsing with the prewash light flashing twice.

The element was O/C so I have replaced it with a new one and thought job done!

This afternoon I put the machine on a hot wash at 90 to clean it and after about
an hour it pumped out nice and hot but immediately tripped at the
rinse stage.

Element is still good resistance.

Now the machine trips as soon as I try and start it.
I suspect it is tripping now when it tries to run the main motor...initial pump out seems to work and than bam.

Door light is good and I have also swapped the motor both were/are good motors.
I have a megger but cant find an obvious earth fault...

Any advice would be most welcome as these are still fantastic machines
and I pretty well out of ideas.

Thanks in advance!

 

[rocks1]

Have you tried to disconnect the heater and pres switch or mains supresser. I take it that it trips straight away now that's wot I would do. Heater could go down after heating. There's not much left that would cause it apart from wiring.

 

[cjapeterborough]

Thanks for the reply.

The last thing I tried was swapping the motor and then starting a cold wash.
The dials clicked round,then the door light,then the drain pump had a go for for a few seconds and then it tripped.

I think it is tripping as soon as the motor starts to turn the drum.

Will investigate more tomorrow but havent made myself very popular
this afternoon regarding the TV,s and PC' going down every 30mins or so
whilst I try and work out whats going on!

The element was brand new and still showing 27ohms.

With the old element o/c it wasnt tripping just not heating....

Will commence battle again tomorrow and recheck all the wiring and mains supressor.

 

[Psykor]

Is it possible to isolate the appliance that is tripping the circuit with one of those RCD socket thingies? Or is that only for outdoor equipment..

I know I'd be really annoyed if the PC or TV kept going off every so often, especially the computer since it takes ages to boot up and you lose your unsaved work.

 

[Leccy758]

For earth faults on these I generally look at

Motor 'Brushes and windings especially if allowed to get a bit damp'
Heater
Mains suppressor
Wiring loom
and on the odd occasion moulded plug.

Have you tried running it or doing a insulation resistance test with the motor, heater, pump etc disconnected then reconnect up one at a time to see what happens
as Psykor suggested we use a plug in RCD (or disconnect the earth and run it through an multimeter on mA setting) to try and minimise the the trip nuisance and find what is dumping current down the earth.

 

[cjapeterborough]

Leccy thanks very much for your input.

I have investigated some more using the Megger I have.

Applying 500V and monitoring at the plug I have noticed that with the
motor disconnected and everything in or out of line apart from the motor gives >3GOhm.

With the motor in line and then activating the on/off switch
shows the value dropping to zero and then recovering to about 40 MOhm

I also tried with water in the drum -no change and element fine.

The machine will drain without the motor plugged in.

The other motor I have if anything is slightly worse giving about 25 MOhm
after the switch on.

Both have good brushes and came from working machines.

It will now trip however as soon as the on/off switch is activated.

I have noticed some drips underneath the machine and am wondering if
I have sprung a leak somewhere which is effecting the motor wiring etc.

I dont like to be beaten so will investigate more tomorrow before taking
a large hammer to the thing!

Thanks again.........

 

[Leccy758]

I have found it quite common for motors to go low resisitance and cause the RCD to trip when they get damp (often due to condensation after a leak or bad siting).
Normally I let them dry in a warm room for 24 hours and they are ok.

 

[cjapeterborough]

Just an update to say that I have fixed the problem at last!

On closer investigation I discovered that the vent pipe that runs from the
antisyphon drain chamber back to the soap box was leaking.

Overflow only happens when the pump is running at its fastest so any water
ends back in the drum via the vent to the soap box.

It baffled me for sometime as gravity can really fool you as the drips took
sometime to make their way round the drum and then land on the main motor.

One of the motors has now dried out and insulation resistance has gone
up to around 0.2GOhm with very little change when the on/off switch is
activated.

This explains why the machine worked fine up to the point where it first
pumped out unattended........