the rectangular under the dash light is itself a rocker switch

 

Roger is correct. On the 1988, there should be two rectangular "courtesy" lights pressed into the bottom side of the knee bolster, one on the driver side and another on the passenger side. The clear lens on each of these lights acts as a three-way "rocker" switch. Pressing on the ends of the lens is how you move the switch between the three possible positions. One position is off all the time, another position is activated/controlled by the "light timer relay", and the third position is on all the time. It's very easy to accidentally press or bump the couresty light lenses and switch them to being on all the time (and draining your battery). If the footwell courtesy lights on you '88 are on all the time, the first thing you need to check is the position of the lens rocker switches. Chances are, they have been bumped or inadvertently pressed to the "always on" position.

If changing the light switch positions don't solve your problem, you might have a faulty light timer relay (SIPEA 0679, position #3 in the top row of the fuse panel).

Also, the driver's side door pillar has two push button switches while the passenger side has only one. On the driver's side, one pushbutton switch activates the "key in ignition" reminder buzzer, and the other operates the courtesy lights. If both doors are open, pressing either courtesy light pushbutton will not extinguish the lights, both need to be pressed at the same time to turn the lights off. And quite often the rubber bumper on the door (that contacts the pushbutton switch) will wear out and flatten, or fall off completely, and fail to fully depress the button.

Good luck,

 

Thank you guys. The rocker switch had been bumped on the passenger side. I did not know that was even a feature. Thanks again Rogerspeed and Norseman50!

 

Ha, I too didn't know they existed until the driver side light stayed on all night and drained the battery. I also noticed the glove compartment light (not the removable one on a cord) on constantly. I unplugged it from both ends. What action operates ? Opening and closing the glovebox door has no affect on the light...