I've just had to fix this on my 1.9 DTi, it's at the if you look in the bonet, it's at the front of the gearbox near the battarie, if you follow the thick wire from the + turminal of the battarie it will go straight to it.
I had to remove it from undernieth the car. The wire that goes from the solinoide to the motor is a thick braid, mine had caroded and then burned out, I replaced it and now it works fine.
Guy
February 2009