The shift light means absolutely nothing. Some owners just pull the bulb to avoid the irritance.

Is your brick a manual or an automatic? Regardless, if the OD doesn't engage at all when you press the button it is probably either a faulty button, gummed up solenoid (on the OD), or a bad/old overdrive relay.

As a first step, pull the relay and resolder it (see the 700/900 FAQ Relay Section for more info) or just replace it. I favot the latter since you can get these parts from online sources like:

http://www.importeccatalog.com

for about $30, but resoldering works as well and costs about $0. You can also just take the relay with you to a junkers and pull one out of a dead brick.

The overdrive relay is the white, square, tall relay located in the middle row, far right side of the relay board (behind fuse panel in back of the asshtray).

If not the relay then the check the button, if its not the button then its probably the solenoid needs tobe cleaned up.

good luck,
rt