Need some assistance from electrical gurus..

ZombiePopper · Mar 11, 2014

I'm stumped and need input from some of you electrical gurus.
Its the headlights that are being problematic;

ive got; front turn signals (bumper), rear t-sigs, brake lights, t-sigs on fender indicators, emergency flashers, dome light, trunk light, kick panel/map light, oil pressure (idiot light), alt guage, (fuel guage is sporadic but I'll be replacing sending unit shortly), ALL work as they should.
Ive checked all 4 headlights and all light up (out of the car off a spare battery), checked all fuses and checked and replaced them anyway, I've traced the wires all the way up to the bulkhead and they're in great shape (no cuts, frays, shorts, etc.)

But I have no headlights highs or lows, I'm thinking maybe the headlight switch?
Anything else I should look at????
(I recall a relay in the dash?).
Any advice would be appreciated, thanks guys!

Hemi Rebel · Mar 11, 2014

Check the dimmer switch on the floor next to your left foot

aldal · Mar 11, 2014

Did you check if you are getting power to the headlight connector with a test light? Good ground?

ZombiePopper · Mar 11, 2014

The dimmer switch is unscrewed from the floor pan but is still plugged in.

At this point, I'm assuming I'm not getting power to the headlight terminals, I'll verify that tomm though.

grounds appear good...car starts runs and drives fine, I am missing 1 ground strap from the block to the firewall (haven't gotten to it yet)

bigmanjbmopar · Mar 11, 2014

Dimmer has to be secured to metal for grounding, but if that doesn't work do you have another headlamp switch?

ZombiePopper · Mar 11, 2014

Ah, I wondered about that, duh! Figured itd need a ground but didn't think about the dimmer switch being grounded also.
Ive got an extra dimmer and headlight switch if need be.
ill secure the dimmer and see what happens tomm., fingers crossed

67 B-body · Mar 11, 2014

bigmanjbmopar said:
Dimmer has to be secured to metal for grounding, but if that doesn't work do you have another headlamp switch?

You sure about that???

Hemi Rebel · Mar 11, 2014

Iirc the headlights high and low beam circuits ground through the dimmer switch. I dont have a diagram in fron of me and its been a few years since I messed with this. Last car was a friend of mines 68 roadrunner. When you switch the lights on both high and low beam circuits are powered up and the floor switch toggles the ground between the two.

67 B-body · Mar 11, 2014

Hemi Rebel said:
Iirc the headlights high and low beam circuits ground through the dimmer switch. I dont have a diagram in fron of me and its been a few years since I messed with this. Last car was a friend of mines 68 roadrunner. When you switch the lights on both high and low beam circuits are powered up and the floor switch toggles the ground between the two.

I just checked a 67 schematic, and didn't see any grounding on the dimmer switch.....
Looks like the dimmer controls the 12V+ by using power from the headlight switch (Light Green Terminal "H") Then from the dimmer switch on either the Red or Black lead depending on dimmer switch position. From there it goes through a bulkhead connector (x and W) continuing with the color codes Black and Red, and finally landing at the Low beam light connector.... From there it will go to the high beam light...... Running in a parallel circuit from the first low beam, it travels across to the second Low beam / High beam assy..

One thing to check would be the grounding of the Black-W/tracer wire that joins all 4 light bulbs.....

Gpuller · Mar 11, 2014

I say throw in the new dimmer (grounded) and the lights will work.

67 B-body · Mar 11, 2014

BTW,,,, If your ground (-) cable is going from the battery to the engine, you WILL need the ground strap from the engine to the firewall.... This gives the body the ground required to operate things such as headlamps...

- - - Updated - - -

Gpuller said:
I say throw in the new dimmer (grounded) and the lights will work.

Why????
With a meter you can ohm from the input side to one of two output points,, then switch your lead to the other output side and push the switch...
Test the thing first...

Hemi Rebel · Mar 11, 2014

67 B-body said:
I just checked a 67 schematic, and didn't see any grounding on the dimmer switch.....
Looks like the dimmer controls the 12V+ by using power from the headlight switch (Light Green Terminal "H") Then from the dimmer switch on either the Red or Black lead depending on dimmer switch position. From there it goes through a bulkhead connector (x and W) continuing with the color codes Black and Red, and finally landing at the Low beam light connector.... From there it will go to the high beam light...... Running in a parallel circuit from the first low beam, it travels across to the second Low beam / High beam assy..

One thing to check would be the grounding of the Black-W/tracer wire that joins all 4 light bulbs.....

Yup. Your right. I just googled the diagram. Its the same for 68 too. dont know why I thought the dimmer was on the low side of the circuit. Like you said, test the circuits. See where you have or dont have power and ground.

vin_vl29u · Mar 11, 2014

The weak link is usually the dimmer switch. Like stated above, check the light green wire for power with the light switch on, one of the other terminals should have voltage. Click the switch, the other side should have power. I've never seen a dimmer switch that needed to be grounded, like most switches, they just turn things on and off. But anything is possible. Ed

A383Wing · Mar 11, 2014

bigmanjbmopar said:
Dimmer has to be secured to metal for grounding, but if that doesn't work do you have another headlamp switch?

no it doesn't...it can hang from the car and still work

ZombiePopper · Mar 11, 2014

Thanks guys, y'all have given me some directions/things to check, I'll crank up the multimeter and see what I have/don't have tomm. Starting with the ground strap since my - batt cable IS bolted to the block.

bigmanjbmopar · Mar 12, 2014

A383Wing said:
no it doesn't...it can hang from the car and still work

Yep I stand corrected, checked again and there is no shown ground connection at the switch, it's just bolted to the floor of the car which is grounded overall lmao

You can at least rule out the high low beam switch with an ohm meter. check the switch disconnected from the harness first if it checks good I would go to the dimmer of headlight switch.

ZombiePopper · Mar 12, 2014

After pulling my HL ground and cleaning reinstall, installed a ground strap, testing dimmer switch and nada, swap dimmer switch and boom, highs and low beams!

BUT, now I've got another problem, now the damn car won't start and stay running wth?!?!
if I turn the key to the crank side and hold it, car seems to start and run, but as soon as I let the key go, it dies.
If I just bump the key like I do normally to start it, it fires for a second and dies instantly.
i haven't changed anything other than the dimmer switch and added a ground strap (from head on passenger side to bulkhead) so I'm not sure what's going on, I swear this car messes with me...

can the ignition switch just go bad like this? What else should I look at?
As always, I appreciate your guys assistance!

Gpuller · Mar 12, 2014

67 B-body said:
BTW,,,, If your ground (-) cable is going from the battery to the engine, you WILL need the ground strap from the engine to the firewall.... This gives the body the ground required to operate things such as headlamps...

- - - Updated - - -

Why????
With a meter you can ohm from the input side to one of two output points,, then switch your lead to the other output side and push the switch...
Test the thing first...

Beacause the switch is junk thats why. Seen it many times, my car just last summer.

Good to hear you got your lights working zoombie.

bigmanjbmopar · Mar 12, 2014

Well high low was bad so why not replace ignition as well? seems strange on that one though get fire then dies? hmm sure it's not a fuel problem or a choke issue?

ZombiePopper said:
After pulling my HL ground and cleaning reinstall, installed a ground strap, testing dimmer switch and nada, swap dimmer switch and boom, highs and low beams!

BUT, now I've got another problem, now the damn car won't start and stay running wth?!?!
if I turn the key to the crank side and hold it, car seems to start and run, but as soon as I let the key go, it dies.
If I just bump the key like I do normally to start it, it fires for a second and dies instantly.
i haven't changed anything other than the dimmer switch and added a ground strap (from head on passenger side to bulkhead) so I'm not sure what's going on, I swear this car messes with me...

can the ignition switch just go bad like this? What else should I look at?
As always, I appreciate your guys assistance!

ZombiePopper · Mar 12, 2014

Good question,
Car ran like a top yesterday, cranked up and ran great, just last night.
i ended up flooding it before I stopped messing with it tonite. I've got fuel in my clear fuel filter and the fact that I flooded it makes me think fuel delivery is okay (?) choke is open.
def odd, never had any probs with the ignition switch before now, just surprised, its out of the blue (makes me wonder if there's a connection between lights???)
plus if I hold the key it seems like it starts and runs like normal (til I let off the key).

Need some assistance from electrical gurus..

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