Low steady voltage flickering to "INST" fuse? 69 GTX...

I'm replacing the factory AM radio in my 69 GTX with one of those repro AM/FM thumbwheel units. There are apparently 2 voltage leads going to the radio, same for old and new. One is for when the ign. switch is on to run the radio, the other one supplies power to light the dial only when the lights are on.

My dash lights have never worked, and checking at the fuseblock I get a very low steady flickering from 0-to-2 volts at the "INST" fuse. This is measured from the supply side with the fuse removed.

SO... where's my voltage? I tried to trace this orange feeder lead out via the service manual, but it just says "To Body Plug". Any ideas?

with it (dash lights etc) only being lit up when you pull the headlight switch on I would assume that power for that circuit originates there. I'd pull the HL bakelite connector & check the terminal at that end & first I'd confirm the crimped connector on the back of the fuse box for that inst terminal/wire has good continuity.

The dash light fuse will get voltage from the dimmer switch so your test light will brighten and dim with the dimmer switch being turned.

Thanks guys. Stump: I am seeing the same 0-2v flickering out of the 2nd lead supplied to the radio...

If your dimmer is part of the headlight switch then the switch needs to be replaced. If the dimmer is separate the the dimmer can be checked for voltage in and voltage out to see if it's good.

Okay: YES, that makes sense! I will check it out

That lead would be for the light in the radio, to dim it with the dash lights.

EXACTLY, Super, and I'm trying to figure out how to get it the voltage it needs. So far, adjusting the dimmer switch has no effect at all on that lead. It should!

Dimmer is either the coil part of the headlight switch or a separate switch either way the switch is bad. Easy test is to apply power form a live fuse to the inst fuse and see what the dash lights do. They should be on full brightness.

Stump: Again, you guys have not let me down. I gotta get out there and check this out again... right now it is (seriously!) 105 degrees out here... and even hotter in that metal box I call my "shop"... and still hotter in the next few days
Just think of the hot box in Cool Hand Luke.
I can jumper right over from a nearby 12v fuse onto that lights feed.

What ya gonna do when it gets hot out? I just spent the afternoon replacing the clock spring in my 03 Ram in the driveway. I know it's only 101*. I guess the main thing is the Ram is my daily driver and I had no choice but come on now.

I still get out there Mornings y'know