in my 87 and my 89 my interior light is whacky. it doesnt work anymore and it used to. not the map lights, the one with the little swith that comes on when you open the door. my 89 is base so it does not have map lights which means no interor light which sucks. it once in a while decides to work (both cars) and im not sure what the hell is up with it.
thanks!

 

Check the switch and look for brittle wires as well. If that doesn't work look for rust in the light socket, mine had that problem the bulb was not making a good ground.

 

Lights? who needs light.. does your engine run? GREAT

just joking.. well i guess first the the bulb.. but i'm gonna assume you already did that.. the yea.. just look for a wiring diagram and trace it back..

could also be the door switches

 

Remove the switch at the base of the door opening. (One screw.) Pull off the wire connected to it and touch it to bare metal. If the light comes on, the switch is most likely corroded. It'll be obvious how it works once you have it out. Just clean the contact with very fine (like 600 grit) sandpaper. That fixed mine.