Confusing door jamb switch

[Titans61]

87 gmc. Has dome lights and courtesy lights that work when either door is opened. It's great, works like you'd want it to but the thing is, if the door jamb switch works the way it should, than why does it works as follows; two wires come out of driver side switch, tan and white while only one comes out of passenger side switch.
If I connect the tan wire to the ground bus bar than the lights work like I mentioned before. Remove it, it stops working and hook it up to what I believe is the key alarm switch wire (I say this because the wire is also tan and it's the right fit connector) and it also stops working.
So what gives? I should just accept this and move on but this is completely baffling since I've been trying to get the key alarm to work as well, so if anyone has any idea on how to get that to work that'd be great.

 

[Matt69olds]

Tan is the ground trigger for the key-in-the-ignition buzzer. White is the courtesy lamp ground. That’s why there is only one wire on the passenger side.

My Olds has a drivers side door jamb switch with 3 pins. It’s unique to those cars. There is a white wire (courtesy lamp) the aforementioned tan (key buzzer) and a white/black tracer that is the ground trigger for the lamps in the floor shift console. I don’t know if Chevy used the same door jamb switch, I know Buick did with the skylark/gran sport. That switch was only used from 68-72, then they went back to the usual 2 pin design. The 3 pin has recently become available in the aftermarket, and is expensive!!!

Why GM decided to isolate the interior lamps is beyond me.

 

[AuroraGirl]

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