Headlight switch.

[Kern Dog]

Hello,
I have a 72 Duster out back and can't get the headlights, turn signals or taillights to work.
The car sat for years before it came here. Long story short, this was a project for my brother in law who later lost interest and sold it to me.
We put it together on the cheap so there are parts in it that were junkyard fresh. One of them is the underhood wiring and the instrument cluster.

The headlight switch in the instrument panel has a tang on the housing which looks like it is meant for a ground strap. I see nothing like that inside the dash frame. I used to get a lot of parts from the self serve junkyards so this panel could be from a 73-74 model. I don't have a factory service manual for the 1972 models and the 1971 book that I have shows different wire colors on the bulkhead plug than I have here.
Using a test light, nothing forward of the bulkhead plug gets power. None of the taillight sockets do either. I tried another headlight switch but it too has that tang on the housing and I wasn't sure if it needed to be grounded.
Did the '72 models come with this type of headlight switch and somehow the ground wire got lost on this one?

 

[nutz]

headlight switch ground threw the hold down bolt for the gage light dimmer ...if its mounted in a plasic dash would need the ground

 

[townsend]

If the gauge cluster has a egr lens and a seat belt warning lens then it came from an Abody made after January of 1974.
OEM switches for Abodies didn't have the ground tang but many aftermarket switches did.
Is the fuse box white or black?

 

[Kern Dog]

Fuse box is white, I believe. I'll know tomorrow. The instrument panel in there now has the receptacle for the seat belt warning but not the EGR. The round blank under the temperature gauge is where I thought the EGR light would be.
I have a small collection of headlight switches, some have the ground tang, some don't.

 

[67Dart273]

I would guess not all years had the ground wire on the switch. The switch had to be grounded, even through the dash, for the dome lamp to work "on the knob."

Headlight switches fit a million models for years and years.

Tail/ park and head battery power comes from two sources.

Headlights only power comes off the black wire splice in the ammeter wire "welded splice" not fused, direct to B1 terminal on the switch.

Tail, park, and dimmer controlled dash lamps comes to B2 from the fuse panel. Additionally, after the dash lamp power leaves the dimmer, that power then goes to the small INST fuse in the fuse box, where its' fed out on orange wiring

Do hazard and brake lights work?

Brake lights come from the fuse panel "hot buss" from a fuse, fed to the TS switch, so they should work all the time.

Hazards work? They are fed from a hot fuse through the separate flasher, so they also should work, regardless of key position.

I would check for power at B1 and B2, then move to the dimmer switch and see if it's there. AFter that it could well be a mismatch of harness parts, or just plain poor connections in the bulkhead connector

 

[67Dart273]

You can download a 72 Plymouth manual, free, from MyMopar.com. Not sure anymore, I think that came from AbodyJoe. Several of the manuals over there came from guys on here.

 

[Mattax]

turn signals

Turn signals need the key in run or accessory to work.
The hazard switch will power those bulbs with the key switch off.

My general sense is that 73 and 74 wiring is very similar except for the addition of the seat belt interlock. '75 and '76 each are pretty unique. I tend to think of '72 as more like '71 because the horn power comes off the main splice rather than getting a fused circuit.

 

[Kern Dog]

Partial success.
The headlight switch has that tang so I added a short 18 gauge ground wire…

It runs to the underside of the dash frame to the right of the fuse panel.

Everything lights up. I had to make adapters for the turn signals since the 69 signals have terminals like this:

The wire harness has terminals like these:

The 69 lenses have ground tabs on the side of the sockets.

If they are touched to negative, it all lights up.

I don’t know if the brake lights work. The taillights don’t. I’ll test turn signals next.

 

[Kern Dog]

I have power to the trunk!
I did see that the taillights do work. The turn signals in back are faint but do work, the left side is not consistent. The right side only get a brake light and turn.
No turn signals up front, they stay lit but don’t flash. My guess is the turn signal switch is to blame.
I’m happy to have the front working though.
More work to do…
Cheers.

 

[Mattax]

The headlight switch ground should only be for the dome light

Its redundent when installed into a metal dash.

A lot of our cars ground the parking and tail lights to the body. The headlights are grounded by wire.

Turn signals will only blink when there is enough current through the flasher unit to heat the bimetal.

 

[Kern Dog]

How can the switch be grounded if the instrument panel cover is plastic?

 

[Mattax]

How can the switch be grounded if the instrument panel cover is plastic?

The switch metal to instrument panel metal on most.

Is yours different?

 

[Kern Dog]

Mine is a 72 so maybe, maybe not.
I tested the lights with the instrument panel resting on the column so technically, the back side of the housing wasn't touching the dash frame. Mine is a stamped steel housing while earlier units are aluminum.

 

[Mattax]

The dome lights are the only item in the headlight switch that needs grounding.
Disconnect the headlight switch ground wire and parking lights should still work.

 

[Mattax]

here's somebody's '72 dart instrument panel

 

[Kern Dog]

The dome lights are the only item in the headlight switch that needs grounding.
Disconnect the headlight switch ground wire and parking lights should still work.

The parking lights already work.
I'll repeat: The grille parking lights work. The headlights do too. They barely flash with the flasher button pulled but neither blink when the turn signals are tried.
The taillights light up, the flashers barely light up. The right brake light works, the turn signal does too. The left only gets a tail light but no brake lights or turn signals.
I have juggled 1157 bulbs and have seen no change. The LH sockets or wiring may be to blame. I have spares I can solder in to get it working.
There is no dome light in place. Grounding the switch has no negative effects, does it?
The dash and all that is attached to it will get restored....

I wanted to get all the stuff working before I dig in and paint it all.