[carl0s]

Yes it did seem to be varying its resistance to earth with heat. The resistance across the two terminals was consistent at 43 ohms though. I had read that they could hold damp, which would explain varying resistance to earth with heat. I tried baking the element in the oven for an hour but this made no difference.
I bought a new element, and what do you know, it works.
I’m quite surprised that the element could appear to work, heat up properly, yet cause this fault.
I’m surprised the machine can sense something subtle like this. I sort of expected it would just switch mains across the relays without much finess or monitoring of the mains power to the element. I know the drum motor is 3 phase brushless induction with fancy control, but I didn’t expect a similar degree of control of the heating element.
I also would have thought an appreciable earth leak would trip the RCD in the consumer unit.
Anyway I did more tests and the bad element did show some conductivity between its terminals and outside metal bits, with less resistance as it got hotter. The new element shows open circuit / infinite resistance.

[carl0s]

electrofix wrote:could be earth leakage on dryer element

Dave

Hi Dave. Thanks for this.
I tested earlier, and I measured infinite resistance / open circuit between heater AC lines and earth.
However, after repeating the failure just now (another attempted drying cycle – not sure how long ago it failed.. could be 15 to 20 minutes ago) , I measured less than 0.2MOhm (a tenth of what is stated above), which was gradually increasing. 5 minutes later it’s up to 2.2MOhm.

I’ve got the element out and am testing it while watching telly, and readings are all over the place though. 9 – 10 meg one minute, 2.2 the next.

It’s a 1.2KW element and shows 43 ohms across it, which would be correct.

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