Symptoms: None of your interior power locks work. Your door's keyholes do not activate power lock system. Your fuses are fine. Your remote keyless entry system still works and all of your doors respond to it.
Probable Solution: Credits to this guy http://www.bimmerfest.com/forums/sho...882&highlight=
and NomadE30 for helping me out.
The problem happens in older E36s with rust along the bottom, allowing water to get under the carpets. It causes 7 Red/Green wires inside a black plastic connector to rot out completely, leaving no electrical connection. To gain access to this plug, you'll need to pull up the carpet under the seats until you expose a hard white plastic coverish thing located underneath the carpet, just in front of the drivers seat.
At this point, I assume you are kneeling by the driver door opening, facing into the car. The white coverish thing will be towards the front of the car (your left) and the black plastic connector will be just right of the white cover thing, and towards you. The black plastic connector joins 7 Red/Green wires together and is attached to the chassis via a plastic, nutless bolt.
If you think that the wires are fine, give them a tug. You may be surprised to see that all 7 of the wires might fall out. My black connector was flooded with green copper oxide. I stripped all the wires down an inch, twisted them together, put a plug on them and then sealed the deal with tons of hockey tape and electrical tape.
Fixed my locks!