Hi Paul, do you have the manual, or pull the machine out slightly to access the top.This will tell me the Diplomat model number, should be something like ADP4520 etc.You are correct, it is the thermostat with switch combined and when you switch on the mains the over gets warm,sometimes the red neon is on also.If you can resend the model, I can tell you the part number you require.If it is a range cooker.Pull all the control knobs off,there are 2 philips screws,one at each end where you have pulled the end knobs off.Pull out the centre divider,take the side or top screws out to remove the hob units,take the back covers off and all cover plates at the top.It is not an easy job and worth the price of an engineers visit.Hope this helps. All the best.
FOXY
August 2008