Chevrolet Astra DTI starter problem

The MSJ is idem to the previous one, only to clarify the mythov to be observed. My astra 2 days ago has problems with cold (it is diesel, Ecotec 2.0 16v engine). I already locate where the preheating and timer are the timer, but I wanted infromacion on how to disassemble these pieces and their operation test. thank you. greetings.-

Tests to perform the heater, take 1 with a cable in the thread from the heater to negative and the other pole + must be put to red alive. Azlo with the 4.
2º -Cog a voltimeter or bulb of 12V, connect it to the sheet that joins the heater and give key contact (the bulb remains on and after a while it goes out - well o/the voltimeter brand 12v and the 5 seconds or so marks 0 - Either.

Note: The other stretch of the bulb or the polyimeter put it to negative.
If something of this does not happen.