I experienced this problem with my '96. The manual-on setting would not work unless I maintained constant finger pressure on the switch. I removed the whole assembly by first prying off the two lenses. This exposes the two screws that hold the assembly to the roof. Turns out there's no discrete switch module. The assembly is built around one large circuit board.

I then removed the center plastic rocker by pulling it straight out. Be careful- there are 3 spring-loaded contact pins behind the rocker. (Unfortunately, I broke off one of the plastic ears on the rocker doing this.) I found the problem is that, over time and with use, the springs become compressed and so do not exert sufficient pressure on the pin to maintain proper contact with the board.

My solution was to clip a small (1 mm) length of thin gauge copper wire, and then insert this into the hole of the rocker that holds the contact pin. Then I put the contact pin into the rocker. This effectively extended the length of the pin so that it makes contact with the board. Then I fitted the rocker back into the assembly. Lights work again.

Leon