Washing machine fault

[Ben Blaukopf]

Washing machine (Bosch Exxcel WFX2868, 7 years old) is tripping the RCD after a few minutes - some time after the motor starts up. Once it has tripped once, it will trip again immediately if you turn it on, but the short eventually clears. If you switch it to the drain cycle, it will turn on and drain just fine.

There's about 2cm left on the brushes, and they seem to be contacting fine (measured 2.4 ohms between brushes, no idea what the nominally correct value is though). I measured all terminals on the motor against earth and got no hint of a short.

Any ideas?

[Bob Eager]

I'd suspect the heater...corroded or whatever. Might fit those symptoms.

Can you try other operations (e.g. cold wash, rinse) where the heater will not kick in?

[F]

Try the forum at

helpful.

[Brian Gaff]

How worn is the comutator though, often the debris here can give unacceptably low resistances in some motors. Don't know spcifically about this one though. I know those old vaccuum motors Hoover used were prone to this.

Brian

[Brian Gaff]

Yes that is a possibility. Hard water can tend to insulate them from the water so they get too hot and split, though normally if you leave it till the water gets cold it will kick in and blow again.

Brian

[Andrew Gabriel]

A corroded washing machine heater can also trip and RCD when it's not running, through a neutral/earth leak, although it's more certain to do so when it switches on. Trying to run the machine on the same program, but with both heater terminals disconnected (and well insulated and tied out of the way) would be a reasonable confirmation. (The program probably won't run fully as the water won't get up to temperature, but it will avoid tripping the RCD if the heater is the cause.)

Sometimes the heater casing gets damaged as the drum bearing wears and the inner drum drops, causing it to start rubbing on the heater. As I mentioned in another posting recently, check for this by seeing if there's much relative movement between the inner and outer drums by trying to lift the inner drum at the front.

[John Rumm]

As the others mentioned, heater would be my first suspect. May not be applicable to your model exactly, but this Bosch heater replacement procedure might be of some relevance:

[Graham.]

You are unlikely to be dealing with a short to earth, much more likely to be slight leakage, hundreds of k ohms. It does sound as if it's the motor from what you say. check for carbon deposits in the commutator and the brush carriers.

[The Natural Philosopher]

I had a machine that did this. striped it down to the drum motor and stripped that. One of te commutator sigments showed 2k to the armature metal - recon motor and it sorted it.