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My 14yr old Ariston AFA250 has developed a puzzling fault. When it’s filling up, it trips the mains RCD. As part of my fault-finding, I bypassed the trip by putting the dishwasher on a testing extension I have that has no earth connection (It’s ok – I know what I’m doing!). What’s happening is that with the machine drained, the chassis is at zero volts wrt earth. Once the machine is started and the water in the tub just becomes visible as it comes through the strainer holes, the chassis jumps to a very lethal 191V AC. This is roughly halfway through the fill cycle. Put it back to drain and as soon as the water level drops below that point, the chassis drops to zero volts again (or just a couple).
It’s obviously the water level somewhere reaching a live part… but where? The water level doesn’t get high enough to reach the heater element (not that that would be live during the filling cycle anyway) or the temperature sensor. So, what else could it be ?
Thanks in advance!
Re: A shocking dishwasher problem!
Heating element or circulation pump motor earth leak. It’s one or the other my guess.
Re: A shocking dishwasher problem!
Well, the heating element was my first suspect too, but the tub goes live rapidly at a point where the water hasn’t reached the element yet. The element runs around the outer edge of the tub and is a good 1.5cm higher than the water level when it goes live.
Also, unless the element is switched on the neutral side, there won’t be any voltage on the element during the fill cycle anyway.I hadn’t considered the circulation pump motor for a similar reason, namely that in terms of water level, the pump motor is pretty much ‘below the waterline’ all the time. The symptoms of it going live at a specific water level doesn’t fit well with a motor whose physical environment isn’t changing at all.
It is definitely related to the level of the water, so, somewhere in the feed system there is a component, a sensor maybe, that is erroneously live and passing voltage into the water (or the chassis directly) once it becomes wet.
I can see me having to take all the damn panels off it and pick my way through with a meter….
Re: A shocking dishwasher problem!
Hmmm…. seems I was wrong and you were right ! I had another go at it this afternoon and, with my non-earthed extension in place to stop the house mains tripping, I found that the chassis did not become live when I had disconnected the heating element.
Therefore, the element must be switched on the neutral side. I didn’t think the water level rose enough to make contact with it, but I’ve just realised that the water only has to reach the mounting plate that is electrically at the same potential as the element itself.
Weirdly, when I ran the machine with the heating element disconnected, it filled part way then immediately emptied and gave me an LED ’02’ error. When I reconnected the heater, it filled normally and started washing…. strange !
Anyway…. new element on the way and hopefully, old Wishywashy lives on !
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