first of all id like to thank you for your reply.

every thing was working fine before all this, however why wouldnt the petrol cap button work, its fuse isnt blown. he did not go near any of the other electric components other than the stereos.
the problem is that he cannot locate the fault as all the wiring is perfectly done, and all the fuses are not blown. i don't want to take it to VW because they charge £58 per half hour, and you still have to pay even if the problem aint fixed. (daylight robbery this is)