Miele Dryer T358?

Dear all,
I have a Miele T 358 and it is tripping the main differential breaker in the house. I have opened it and completely cleaned all the inside.
Would anybody have an idea as to what part could be causing the earth leakage.
For me it could be the motor or the heater. Does the motor have brushes that could need to be replaced?
Also what role does the carbon brushes running around the outside of the drum play?
I have yet to try and run the machine with no heat to confirm the problem is with the heating element or not.

I really don't want to replace the machine because sticking your nose in it you can see just how well made his machine is.

Sorry for so many questions but I want to try and isolate the problem and then try and get parts..

Thanks for any help...