Golf Electrical Problem

[SOF]

Hello
I own a Golf 2002.
I have a strange problem witch vanished 5 min after I'm drifing the car.
description:
When I open the car doors the internal light does not work, and when I open the switch and trys to get the windows down, they does not work.
also the electronic lock of the luggage compartment does not work but the door central lock does work.
After a few min I'm starting to hear a contact opening and closing, with that also the internal light of the car are flasing on and off the windows and from,time to time I see indication of an open door.
After some time it all become stable, and everthing is working ok again.
I was able to find the unit which the vibrating contact noise came from.
The Unit is a small box with electronic board inside.
The part number of the Unit is 1C0-959-799.
it is located beyond the internal fuse box.
According to a search I did I understood that this unit is responsible for light alert internal ligth...
my question is:
I don't have the electrical drawing of the car, so I really check that the units receives evrithig it needs.
But according to the symptoms I gave, do you think that unit is faulty?

I don't know how much a unit like that cost but it looks expensive and it could be that it is not the problem.
I would be glad to receive some guidance.
without drawing I feel blind do you know where can I get ones.
Thanks
Ran.S