Let the world see who you are at night. From the October 1993 Registry newsletter
If you do not have a Masters in Electrical Engineering, trying to diagnose electrical problems is always a nightmare. I was working with Jens Vagelpohl on my daily driver (he's got a Masters!) one weekend and he enlightened me (yuk, yuk) on how to make my license plate lights work better and brighter. He took it for granted, but I had no clue, so I took notes knowing it would make good newsletter material.
First, check your bulb in the license plate area. Make sure it is the right voltage bulb and is new (sometimes it gets overlooked during a 6-to-12 Volt upgrade).
Next, get a toothbrush and clean out the bulb area and blow air into it to make sure.
Then, reinsert the new bulb and reassemble the unit.
Now, look at the bottom of the unit (see drawing) and look for the small pointed pin at the lower left side. This is the contact pin which allows ground connection and ensures a good strong light! Use sandpaper to clean the contact point (but don't wear it off completely). This should remove the old dirt, grime, and corrosion to allow for the optimum grounding onto the overrider. While you are there, clean the overrider area also.
Finally, reassemble the unit to the overrider and connect the wires. If you have juice to the bulb, you should have a great light! Remember, you heard it here first...