well...
after "digging" in the wiring loom I found the problem.
Possibly the previous owner try to fixed a problen and create a new one by connecting the wires wrong.
What I got was 3 wires and I knew that one of them is 12v, the other is body ground, but the third was uncertain.
I couldn't even tell if it suppose to be ground or 12v.
and further more, I was curious... how is it, that each door is distinguished on the gauges panel but not by the cab light ?
So... yesterday I was... a man on a mission !!!
Each door switch connect the body ground to the gauges.
Each door lights up different hazard signal (left & right), so the
gauge "need to" distinguish between the switches, but the
cab light "don't care" which door is open and need to lights up
in any door opening case.
so basically, the cab light gets 1x live feed 12V and 2x ground feeds. choosing the "correct" ground done by the switch on the cab light.
One ground is directly from the body (fixed light on), and the other comes from the gauges, after collecting both switches (4 switches in case of sedan) by a technique called in electricity "power or-ing" which done by diodes.
(those diodes are part of the gauges circuit, and if its intersting anyone, I will be more detailed about this simple technique).
first time for me to see such system at car, and glad to find it after 3 hours of searching wire colors at my current dismantled cab.
a repair manual with color wiring diagram could've been great.
Thank you all for your attention and help.
Ezra