I don't know any place but the Bentley Manual - it's worth the cost.
My guess is that you have one or more broken wires in the wiring loom
where it folds around the trunk hinge. Apparently this is not an uncommon
problem, though I've been lucky so far with my 97 328.
I agree with Frank about the Bentley book and the broken wire. What I would
do is loosen the wiring harness around the trunk hinge and start to wiggle
it to see if you can make the light go off and on. Perhaps try it while
inside the trunk with the lid closed, or almost closed. Of course is easier
if you have someone to help you.
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