Originally Posted by cos jon

On the rear there is a copper pad on the section that runs along the width of the boot (the latch conects here too) these can start to get a film on them which stops the contact being made, get some 1500 grit glasspaper and clean them so there bright copper. Also worth doing this to the 4 pins in the boot which connect to the pads.

The front pin switch is a big block near the chassis plate. Its more than likely that the alarm fitter would have put another one on somewhere but it will be on the slam panel somewhere.