In '91 (and should apply back to about 1985, whenever all the accessory terminals on the fuse panel face were moved to the top) the floor lamp is powered (20A "T/L CTSY" fuse) AND grounded through the headlight switch. The ground (at the floor bulb socket) is spliced to the ground for the door switches/dome lamps.
The dome lamps are powered from a separate circuit (accessory terminal upper left corner of fuse panel).
So for what is happening with mine, the ground wire from the floor lamp to switches/dome lamps is bad. Makes sense, as that floor lamp has always been flakey in operation. Typical, ground problem.
Thanks for making me dig out my wiring diagram, now it makes sense.
The dome lamps are powered from a separate circuit (accessory terminal upper left corner of fuse panel).
So for what is happening with mine, the ground wire from the floor lamp to switches/dome lamps is bad. Makes sense, as that floor lamp has always been flakey in operation. Typical, ground problem.
Thanks for making me dig out my wiring diagram, now it makes sense.

