No dash lights in 4 of my cars!

[Kern Dog]

I know this sounds weird to start off with but it is true and may be relevant.
I admit that while I am pretty handy with many aspects of these cars, electrical stuff is still my weak point.
Four cars:
1970 Charger
1967 Dodge Dart
1972 Plymouth Duster
1975 Power Wagon.

All of them have working headlights, taillights, turn signals and hazard flashers.
I have not checked the fuses to all of them, it just now occurred to me as I'm writing this.
I did do a forum search and while there was some helpful tips, I wonder if my situations could be a bit different.

The instrument panel in the Charger had functioning lights when the panel was in my other car. The fuse panel was changed to one with 7 fuses. The panel dimmer was not moved over from the other car, it was in the instrument panel that came in the car.

The original cluster is the one in the middle. The car sat for 24 years before I got it so I don't know if the dimmer is crap.
The other cars....the 67 Dart, 72 Duster, 75 Power Wagon all have had different instrument panels swapped in, I rarely drive them at night so the lack of lighting has not been an issue but I would like to get them working.
The Dart had dead gas and temp gauges. I replaced a sending unit and the voltage limiter and they work right now.

One response to a thread on this had a guy that went through 4 headlight switches before he had one that gave dash lights. All 4 gave headlights and parking lights.
This has me wondering if all 4 vehicles have the same cause for this issue.
I'd appreciate any suggestions on where else to look to fix the cars. The A bodies seem to use the same type of switch for many years, I have 10 or more spares to try. I'm not sure of the unit used in the pickups. I know that the Charger panel dimmer is unique to these cars. If the Charger dimmer is bad, is there a way to bypass it's function to where it gives dash lights but is unable to be dimmed?
Thanks for any help that you can give.

 

[OneWheelPeel]

I went thru some of this with my stock cluster before deciding it was too far gone and I didn’t even like the look of it, but diagnosing it helped me learn a couple things. One problem was the dimmer switch, but I was able to revive it with De-Oxit, and electrical contact cleaner would have worked. That could also help you headlight switches.
I then set up to bench test the cluster, which really just needed a cheap multimeter and a jump box and some wires for juice.
The multimeter will help you check for continuity which we can figure out some of those details if you don’t know them or can’t find info. You would check the switch/dimmer and traces.
The biggest problem on the cluster was the pins that plug it into the harness would get loose and the bulb connections. The bulb connections continued to confuse me simply because everything could be clean and clearly making contact but would not light up reliably even with power directly applied to the traces.

Hopefully some of this is helpful or gets your gears turning.

 

[Kern Dog]

The biggest problem on the cluster was the pins that plug it into the harness would get loose

Oh, I'm quite familiar with those breaking and having to solder them back on. They sure were not made to last with installing and removing the wire connector a few times.
I plan to do the usual testing with the multimeter, check the fuses, change the fuses, etc.

 

[71RRHI]

At one time I had three cars all with no dash lights. My 67 Coronet turned out to be the headlight switch. Makes sense since the headlight and dash dimmer switch is one unit. On my 70 Coronet, changed the dash light dimmer switch. On my 71 Road Runner, I cleaned the bulked connector, changed the engine harness, forward light harness, and the wiper harness for other reasons. As a bonus the dash lights started working. Not sure why.

 

[Kern Dog]

With these four, I have never seen the dash lights work in the Dart, Duster or the truck. Just the Charger when the panel was in my other car.
The dimmer was found to be the problem in many of the threads that I have read on this subject.
Since it is built into the switch with many applications, the owner has to decide if he can live with no dash lights if every other function is operational.
With the Charger, I'd be interested in knowing which wires to the dimmer are supposed to light up when the headlights are ON. I'm guessing a wire diagram would show that. I do have a good service manual to use.
I'll look into this and hope to report back tomorrow with some progress.

 

[Don selleck]

a colored diagram helps out and makes life easier, electrical contact/ motor spray cleaner, fine emery cloth, tiny round file, and a multimeter, plus time and patience. By the time you figure out the first one, the rest should be easier.

 

[F4R/T]

I know you can by-pass the dimmer switch on the dash by jumping wires if you choose to but personally I’ve found most of the time the dimmer switch has failed. There was a gent somewhere that was repairing them, I don’t recommend a repop.
Deoxit will be a good friend get a couple cans

 

[Don selleck]

and i like some dielectric grease used in the right areas very sparingly.

 

[Outlawd]

This thread has me wondering about my own cars, I always make sure the outside lights are in good working condition but not sure on dash lighting. I know the 71 Charger has dash lights that work because I drive that car to work sometimes in the dark. As for the 69 Coronet and 68 GTX I can't remember the last time I drove them after dark but it would be good to know. Now I have a weekend winter project....check and fix dash lights!

 

[YY1]

Check grounds.

Use a jumper to test.

I jump directly from a known good ground to one or more points (free of paint or anodizing) on the cluster cage.

 

[68plymouth383]

@devinism is the switch guru

 

[WileE]

Many of these symptoms can be attributed to bad grounds, loose connections, corroded terminals, internal switch contacts, corroded/bad rheostats, etc. Electricity likes CLEAN. less clean = higher resistance. I once bought a "non-working" cluster for dirt cheap, took it home on my workbench, took it apart, cleaned everything, result ? Everything worked fine and the only added cost was all new bulbs.

 

[72RoadrunnerGTX]

With these four, I have never seen the dash lights work in the Dart, Duster or the truck. Just the Charger when the panel was in my other car.
The dimmer was found to be the problem in many of the threads that I have read on this subject.
Since it is built into the switch with many applications, the owner has to decide if he can live with no dash lights if every other function is operational.
With the Charger, I'd be interested in knowing which wires to the dimmer are supposed to light up when the headlights are ON. I'm guessing a wire diagram would show that. I do have a good service manual to use.
I'll look into this and hope to report back tomorrow with some progress.

Both leads at the dimmer should show voltage with the lights on. If you have running (park) lights, the issue is with the illumination rheostat (dimmer) or the 5amp fuse in the fuse box dedicated to the illumination circuit. Where the rheostat is separate from the headlight switch, you should have battery voltage on the one wire (black) from the switch with the park lights on, something less on the other wire (tan). That wire routes to the illumination fuse, need to verify you have varying voltage at both sides of the fuse as determined by the rheostat. BTW, the yellow wires at the dimmer is the interior dome light ground circuit, nothing to do with the dash lights.

 

[Pete Kaczmarski]

Start simple.....purchase a can of "Electronic Tuner Cleaner" spray and use liberally on the part of the switch that adjusts the dash light brightness. Go back and forth several times. Don't just spray it on the on/off switch. My '59 Imperial has touchy brightness adjustments. This spray should be used and never Silicone or WD40 etc. A friend of mine used WD40 on a power seat switch and later the car had an electrical fire originating from the same switch.

 

[Coelacanth]

I had an odd experience when I was working on my instument panel for Grendel. All my interior green LEDs were working beautifully, then after I was working on getting the LED working for my glovebox light, none of the dash lights would light up anymore when headlights were on. The dome and console lights were still working, but nothing on the dash. I was thinking my headlight switch spontaneously decided to crap out, but I checked the fuses and the new instrument panel fuse I'd installed earlier had indeed burned out. I must've shorted out the housing for the glovebox light while removing & reinstalling it. It's quite easy to short it out because of the way it inserts into the metal glovebox frame. Not sure if this helps...

 

[Kern Dog]

I started with what will probably be the hardest to diagnose and fix. About 5 1/2 years ago before I got the car running, I changed a few things in the wiring harness though I did use factory parts.
It had a fuse panel with 6 terminals, I put in one with 7. Unfortunately, access to these B body fuse panel sucks.

You open the glove box door and remove a slide cover.

That isn’t so bad but the 7th fuse is now obscured by the edge of the glove box liner.

With my head inside, I could see but since I have a regular sized head, cameras and mirrors are the best I can do.
The fuse in the terminal labeled “Instrument Lamps” gets no power. The fuse itself looks fine.
I’m tempted to relocate this panel to underneath the glove box…

Maybe forward and above the console?
This does not have to be done now though. I have to avoid the trap of The Snowball Effect where one task turns into three months of down time addressing numerous other things.

 

[OneWheelPeel]

My Coronet didn't even come with the box part of the glove box, which makes it easier to get to the fuses but it still sucks. When I added a few things I just jumped straight to a secondary fuse box, not correct but makes life easier and the one I use will light up the fuse position when a fuse blows. I'm still on the fence about eventually running everything thru it.
Is the rest of your dash, meaning radio and ashtray intact? Mine wasn't so I was able to check the back of the stock fuse box easily enough.

 

[Kern Dog]

No power was coming into the 7th terminal…



So just for fun, I hotwired the terminal.

Whoa!

Now I’ll see where the power input is supposed to come from.
“instrument feed” is circuit E1-18T, a tan wire that comes in from the panel dimmer.
Did I find the cause?
I thought that I have the 7th terminal wired backwards but on closer inspection, it is right.

 

[Kern Dog]

Is the rest of your dash, meaning radio and ashtray intact? Mine wasn't so I was able to check the back of the stock fuse box easily enough.

For the most part, it is as it was built. I extended the wiring to the instrument panel so I can have the cluster out while having better access to removing or accessing the wire connector since those brass pins are so fragile.

 

[Kern Dog]

It keeps being weird.
I tried different headlight switches and another dimmer…

The headlight switches all work. One spade is supposed to tie into the panel dimmer, the center terminal.

It is dead no matter what. If I power up that center terminal, the panel lights up.
I feel like a guy on an island looking for gold, essentially using “layman common sense” instead of trained diagnostic skills.