Headlight wiring help .

[mbaird]

In the process of installing a 46rh and new 408 I needed to do some cluster work as well .
Now that it’s back together I have no headlights .
I have installed new headlight switch and dimmer . But have power to both terminals on the dimmer switch in both high and low . And power to high and low bulb terminals.
When I originally restored the car I installed new dash and engine bay wiring .
Could it be I have my ameter feeds crossed up ? Ammeter seems to be working .

 

[mbaird]

68 Barracuda

 

[Mattax]

Could it be I have my ameter feeds crossed up ?

No.

Ammeter seems to be working .

If you placed the red and black wires backword on the ammeter, the ammeter would indicate charge for discharge and discharging battery for batterr recharge.

 

[RustyRatRod]

I would be checking for ground at the headlight connectors.

 

[Mattax]

have power to both terminals on the dimmer switch in both high and low . And power to high and low bulb terminals.

Are you testing with a voltmeter or a test light?

 

[Mattax]

I would be checking for ground at the headlight connectors.

Me too.
Almost guarenteed if the power checks were done with a test light and the light came on, the issue is with the headlights grounding.
With the voltmeter, there are other possibilities but grounding would still be most likely.

 

[crackedback]

Follow the path from dimmer to bulkhead and out to the lights. Go right to the headlight plugs and test light the violet and red in each state from dimmer. If dead there, test light both sides of the bulkhead.

Hot green going into the dimmer, then hot on either violet or red line out of the dimmer means the issue isn't upstream from there..

Grounds would be the other that might be suspect.

 

[mbaird]

Actually I just retested with a test light and am getting power to all 3 headlamp terminals .
I will recheck my grounds but I was pretty careful to make sure all was clean

 

[Mattax]

Actually I just retested with a test light and am getting power to all 3 headlamp terminals .

At the headlight?
One of the terminals is the ground.
The only way for voltage to be at the ground is (a) if the headlight ground wire is disconnected, or (b) a cross wire short.

With (a) you test light provides the connection to ground. In doing so the headlight should have also glowed.

 

[Mattax]

Might be one or might be two but either way the grounds look like this one on CudaAl's '67

 

[mbaird]

Did a continuity test between the ground strap terminal and headlamp plug . Nothing .

 

[mbaird]

Might be one or might be two but either way the grounds look like this one on CudaAl's '67
View attachment 1716470939

My grounds are in front of battery . I looked for others but didn’t find any.

 

[mbaird]

At the headlight?
One of the terminals is the ground.
The only way for voltage to be at the ground is (a) if the headlight ground wire is disconnected, or (b) a cross wire short.

With (a) you test light provides the connection to ground. In doing so the headlight should have also glowed.

No ground .. that is why Im getting power to all 3 terminals? Have to wrap my head around that

 

[mbaird]

I will try running a ground directly from battery to the headlamp terminal . Wiring diagram shows both headlamp grounds interconnect. Should power both then I believe.

 

[Mattax]

Did a continuity test between the ground strap terminal and headlamp plug . Nothing .

View attachment 1716470941

View attachment 1716470942

Lost me here.
If you want to check for continuity or resistance, disconnect the battery terminal. Then take the meter and measure from the headlight connector to the battery ground cable.

 

[crackedback]

I unplug the connector from headlight if test lighting the violet/red wires. Isolates them from all other variables.

Yes, the grounds are typically interconnected

 

[Mattax]

No ground .. that is why Im getting power to all 3 terminals? Have to wrap my head around that

It's possible. Did the lamp glow or did you have the headlights removed their connectos?

 

[mbaird]

Multimeter shows continuity between ground straps and negative battery terminal while disconnected . Grasping at straws here . Does the headlamp ground go through the switch?

 

[mbaird]

It's possible. Did the lamp glow or did you have the headlights removed their connectos?

Had them removed

 

[mbaird]

Lost me here.
If you want to check for continuity or resistance, disconnect the battery terminal. Then take the meter and measure from the headlight connector to the battery ground cable.

I was checking to see if my grounds had shorted to positive somewhere in the loom .

 

[mbaird]

I did disconnect both the grounds from chassis and tested for continuity between them and the headlamp connector . Nada…. Unless I am checking the wrong grounds but I can’t find another . I have done many A bodies but can’t remember exactly . Seemed like the headlight ground was a larger gauge wire with both connected to one terminal . ???

 

[mbaird]

Ok .. so I jumped from negative battery terminal to ground on one headlamp terminal and got lights . Question is why are my ground wires not working? Do I need to ground the switch?
Really not looking forward to untaping the entire harness . They worked last year .

 

[RustyRatRod]

Ok .. so I jumped from negative battery terminal to ground on one headlamp terminal and got lights . Question is why are my ground wires not working? Do I need to ground the switch?
Really not looking forward to untaping the entire harness . They worked last year .

Yes on some the switch has a tang on it that must be grounded. Not all but some and unfortunately, I do not know which years. I'm sorry I'm not more help.

 

[Mattax]

If the connectors are removed from the headlights, headlight switch on, there should be 12 V on the highor low beam and no voltage in the ground wire.

Likewise, connecting a test light to the violet wire as shown should turn on the test light.

Using a test lamp on the ground wire should not turn on the test light. There should be no connection for the electrons to flow through.

But if the connector was plugged in, and you were back probing, then electrons could flow through. In doingso they would have to flow through the headlight's filament.

It's simpler to test with the headlights disconnected.

 

[Mattax]

There is no reason to ground the headlight switch other than for the dome light function.

If there is power in the ground wires with the headlamps disconnected, then there is a crosswire short.

So then you could disconnect the battery and check for continuity between the headlight feed wires and the ground wire. If so, disconnect at the dimmer switch. If it goes away then its between the headlight switch and the dimmer switch (assuming this short only exists with the headlights switched on). If its still there then keep going.