Strange electrical gremlin...'71 Demon 340 rallye dash

Hey gang, long time.....

Two years ago I rebuilt the voltage regulator in my rallye dash with solid state guts. My dead fuel gauge came back to life, and I was happy.......

Last summer, I noticed when I had my lights on, the fuel gauge would peg past full. A bit of fiddling and I found out it was directly related to the dash lights-dim the lights, the fuel gauge went back to normal. Turn 'em up, fuel gauge peg.

With spring looming, I'm working up the courage to pull the dash and poke around looking for what's causing this.

I welcome any hints, tips or past experiences that might guide me in figuring this out.

The older I get, the less I enjoy being upside-down under a dash having 40 year old insulation, dust and God-knows-what-else falling in my eyes.....

my standard answer on this is check your grounds. Electrons start looking everywhere for a path to ground when a good one can't be found. All kind of strange things happen. Install toothed star washers on your ground connections, maybe install a designated dash to body ground strap?

not sure how it's doing it but as you said probably have to pull the dash & see where/how the orange wire dash light circuit is bleeding over to the fuel gauge circuit & in the meantime I'd disable the dash light orange wire circuit to avoid any damage tho you'd think if it was permantntly damaging it it'd have done it by now but never hurts to be cautious. I'd drop the column a bit then drape a rag over the column to protect it then pull the dash (remove a batt cable first)

diagrams are here.
http://www.mymopar.com/index.php?pid=27

looks like red for the high beams and dk blue for fuel.

2 different parts of the board.

my best guess is 12 volts is bleeding over from that red line on the circuit board or your vr.

I don't see how, as they seem to be 2 seperate boards.

do you have the low fuel warning light?
as there is a place where the headlight delay and that relay tie in for power. but again, that should be before the vr.

as said above, the only other common thing is ground.

Quote:

---

my standard answer on this is check your grounds. Electrons start looking everywhere for a path to ground when a good one can't be found. All kind of strange things happen. Install toothed star washers on your ground connections, maybe install a designated dash to body ground strap?

---

Most of the time when attacking a problem like this, your first tendency is to look for a short in the wiring. Most of the time, it is a missing, corroded or painted over ground point. Shorts are easy to find, high resistance grounds a pain in the lower posterior.
Good luck.
BTW, I would start with the new regulator and make sure it is grounded properly.
Craig