OK, I've abandoned the plastering until it gets a bit cooler [and sounds
like the heat may be a cause of the problem anyway...! :-) ]

Have now turned my attention to our faulty oven, as I'm getting ****ed
off with microwaved food! It's a simple built-in gas oven (Electrolux
EOG 660) which all of a sudden has started tripping the MCB of its
circuit as soon as you try to turn it on.

I'm thinking some or other component must have failed, so can't be too
hard to sort...???

I've whipped the top off and with the help of a circuit diagram
helpfully stuck to the top, have been attempting some diagnostics (I've
uploaded a copy he
http://img.photoamp.com/i/qUhqhc2.JPG)

So here's where I am so far:

Have checked the spark electrodes for both grill and oven are clean and
not obviously shorting out;
MCB trips if I try to turn on either the grill or the oven (these are
separate taps);
Disconnected leads L1 and L2 from the spark generator, which I was
suspecting as dodgy - that did indeed allow me to turn on both grill and
oven knobs without tripping, but as soon as I opened the oven door
(actioning the oven door microswitch), that tripped the MCB!

Any thoughts as to how to narrow down the fault?

Thanks
David

The message
from Lobster contains these words:

Any thoughts as to how to narrow down the fault?

My money would be on the varistor.

However, the best way would be to pull the live feed from each
switch/relay in turn until things stop going wrong.

--
Skipweasel
Pay no attention to that man behind the curtain.