AEG Oko-Lavamat 6350

AEG Oko-Lavamat 6350
E no. 605 647 514
F no. 126/749091

Hi,
I have had this machine for 9 years and this is the first time it has needed any attention.

The machine has started tripping the main circuit breaker in the consumer unit, so obviously there is current leakage to earth.
The machine works perfectly when the temperature dial is set to cold wash, or if you select spin only etc.
When a temperature other than cold is selected the machine trips the circuit breaker about 15/20 seconds after the on button is pressed.

I have checked the motor brushes and blown the carbon dust out of the motor – all OK and no earth leakage, brushes still have 20 mm sticking out of holder.
The resistance across the heater element is 23 Ohms with no short to earth.
I have disassembled the thermostat/switch assembly – all appears well no signs of arcing or burnt contacts etc.
I cannot see any signs of arcing or wiring chafing anywhere.

I am reluctant to call an engineer and pay the call out charge, only to be told that the module or something else expensive needs replacing – I would rather put the money towards a new machine.

Am I also right in thinking that this machine does not have a diagnostic function, so unless it is something obvious or the engineer has seen this before I may get into an ad hoc replace parts scenario.

If anyone could point me in towards any other checks I could make I would be very grateful as I would like to fix this machine if economically viable.
Until the other day it has been fantastically reliable and has performed faultlessly for 9 years.

Thanks in advance
Mike