Interior Light non goer!

[dalderton]

I am a new owner of a Mk2 Berlingo from AUS. Amongst some other small problems the interior lights will not work from the door switches even though I have removed the switches and tested them for contact to earth. The lights work from the switches on the light units themselves but not from the door switches no matter where I position the sliding switch on the light itself.
The odometer lights up when I open the doors which leads me to believe that the BSI is functioning and I assume that it is part of the circuit that should light the interior lights. (correct me if I am wrong.)Any ideas on the subject would be appreciated. (Who devised multiplex electrical systems?)
Regards from Australia Dennis.