1969 convertible L46. Gauge lights and parking lights don't work. Headlights, back up lights, courtesy & red dash lights work but no gauge/parking lights. Parking lights do work with directional and 4-way hazard. Battery is brand new, good negative ground. I checked to make sure the gauge lights weren't dimmed. I never drive this car at night, so it's been a long time since I've needed the gauge lights. But of course, I want everything to work properly. I checked the fuse block slots with a tester light, and every fuse gets power on both ends except the inst lmps slot (5A) which gets no power. It seems that power is not reaching that slot. I pulled the fuse and checked with a multimeter. It read 0.02 ohms, so I assume that the fuse is intact. I think I read that power is supplied to that slot by the headlight switch/parking lights circuit. The headlight switch needs to at least be pulled out to the parking lights position for that slot to get power. But if that is correct, and if the switch turns on the headlights, why wouldn't it turn on the parking lights and send power to the fuse block? Did something fry in the headlight switch? I "jiggled" the headlight switch but that did nothing. Every wiring harness has been replaced with new (Lectric Limited) in this car. Any advice? Has anyone had this problem? Am I understanding the circuitry correctly? Should I run 12v to that slot and see if the lights work?

 

I would test by runing 12 volts to one of the grey leads and see if it lights up..... before pulling the dash to check if the dimmer function is working.
I was going to suggest a common ground problem but the fact that the parking lights don't come on make me suspect the light switch.