The only thing I was able to do today was check the light bar was grounded properly. I used a test light on one of the screws, and it lit up, so assuming light bar is grounded ok.
I also checked that l had power to dimmer switch plug.
Got power going to plug for switch to black wire.
The screw could be grounded but not getting a connection all the way to the socket where the bulb is. Unfortunately on the E bodies it isn't possible to test the socket on the over guage lights installed, so I suggest you pull the bar and check for positive voltage at the socket then ground the bar with a jumper and check for them to be lighting up when the light switch is turned on and the dimmer is adjusted.
IF there is no + voltage in the socket, with the lights on, then you know the problem is somewhere back in the line, switch, fuse, wiring, etc.
Check the fuses by putting a test light VOM to each side of the fuses with all switches turned off. I have had fuses heat up at the ends and cause the end of the fuse to break contact and still look good in the middle. This usually happens when the socket is corroded. That is why you check both sides of the fuse, to be sure voltage is making it across the fuse to the wiring on the other side. Doesn't hurt to check the contacts holding the fuse for voltage too while you are there.
