Gauge lights won't dim

[jonstr]

Sorry for the duplicate post (I also put this in the NCRS forum since I'm prepping the car for NCRS judging and wasn't sure which was the best forum for this).

When you rotate the headlamp knob, the gauge lights are supposed to dim. They don’t on mine. I assumed this was a pretty easy fix, and I ordered a new headlamp switch. I got an OEM switch, and it hooks up correctly and everything operates correctly EXCEPT that the gauge lights still will not dim. It seems a mighty big coincidence that the new switch I got has exactly the same problem as my old (apparently original, by the look of it) switch.

Can anyone help me or point me in a direction with the following questions?

1) Is there another component that has anything to do with the gauge dimming function?

2) Is there a way to test the rheostat function on the switch itself?

On that last question, I’ve fumbled around with the wiring diagrams, the switch, and an ohm meter. I’ve located the wire (16 gauge dark green) that controls the on/off function of the instrument lights, but I cannot get it to read variable resistance with either the old or new switch. This would seem to point to a defective switch, except that I can’t get this test to work on the light switch from my ’63 either. That switch does dim the lights on my ’63, so I know it works correctly.

Thanks in advance for any suggestions.

 

[69MyWay]

My best guess is that a prior owner spliced the gauge light wire somewhere in the harness direct to the regular parking lights or headlight wire....or even at the fuse panel. So, no matter what you do, the lights are getting full power to the gauges.

 

[jonstr]

My best guess is that a prior owner spliced the gauge light wire somewhere in the harness direct to the regular parking lights or headlight wire....or even at the fuse panel. So, no matter what you do, the lights are getting full power to the gauges.

Thanks. That was my fear, although at the switch itself, the dark green wire does still control whether or not the lights are on, as it shows in the shop manual wiring diagrams. If I disconnect that wire, the panel lights don't come on at all. But I can see a little bit of 'creative wiring' when I look under the dash. I've got the speedo/tach cluster most of the way out already. I guess I'll have to bite the bullet and pull it the rest of the way so I can see back there. I was just hoping for an easier solution.

Thanks,
Jon