My TDC60 blew the thermostats recently, which I replaced, only to have them blow again.
Ive finally tracked the problem down to the heater relay on the main board which has failed in the ON position.
The result being that the heater is on ALL the time, even when the door is open.
A main board is £100, however i have sourced the same 16A relay from farnell (RS also have them) for £3. You will neet to be handy with a soldering iron though, as this is not a consumable part.
Not fitted it yet, will update when it arrives.
Barry ONeill, March 2006