Duster Headlights not working even with power?

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Justin Angle

Justin Angle

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Hey guys I have a 71 Duster slant 6 and went to flip on my headlights tonight and they don't work at all they've been working ok since I had the car the past few months. I replaced the dimmer switch because I read that was a common cause for headlight failure but no luck. So I got a tester and started poking around and noticed there's power all the way to the headlight sockets and shows power on the back of the headlight itself but still the headlights don't work. Any thoughts or comments would be great. Thanks.
Justin
 
That happened to me i had to replace both headlites, they both failed at the same time? Check for grounds at the socket as well.
 
Bad ground. I think it goes to a bolt on the radiator support in front of the battery. Should be a wire coming from negative battery connecting there as well.
 
Just because you have voltage doesn't mean they'll work. The wires have to pass electrons, lots if them. You can measure 12 volts at the end of a wire the diameter of a human hair, but you couldn't suck enough electrons thru it to power up anything but maybe an electronic part.
It's like a brand new 9volt drycell; it has over 9 volts right, but it can't run hardly anything on your car; like maybe a dashbulb.
So yeah; you need power and ground, but you also need electron flow.
 
Check to make sure you have good ground n that circuit.
 
Ok the ground by the radiator seems fine. I'm having a hard time finding any other grounds but ill look more closely seems like there should be one under the dash on the firewall. Before I drove it last tried to mess with the brake pedal button thing because my brake lights quit working to so I must have bumped something that was loose.
 
If the ground jumper from the battery is properly connected to the core-support, then those other grounds do not affect the headlamp circuit,. But if it's not, THEN the only way back to the battery is thru the firewall to head jumper, thru the engine,to the ground cable, to the Neg. post.
Take a headlight out and jumper the pins to the battery to make sure the dang thing works. If it does then stick it back in and run a ground jumper back to the battery. If it still doesn't work, go back to the bulkhead connector and look for a warm wire; you may have to go all the way back to the dimmer switch light-green supply wire; or the headlamp switch black with tracer supply; or even the #1 splice 12ga black supply from the ammeter guage; or back thru the bulkhead connector still 12ga black,.........
Or just go straight to the bulkhead connector; it's almost always a hi-resistance connection there, or at the headlamp sw itself..
The wire there in question is the big fat 12 ga red from the fusible link,from the battery. On the cabin side this goes to the ammeter, thru it, turns black, and then sneaks off to the #1 splice; then to the headlamp sw then turns green to the dimmer; where it splits into two 16ga wires, a violet and a red , both going out the bulkhead connector again; and then to the headlamps via the sockets. Then thru the filaments to the core support on the headlamp side; thru the core support to the battery via the short usually black jumper sometimes screwed to the engine side of the core support.
If your battery cables are not bonded like the factory cables ,but instead are clamp-on jobber ends, then you may have to disassemble the clamps and clean out the corrosion. The cables are copper and the clamps are supposed to be lead..... which in the presence of moisture, creates a bluish-green compound that can act as an insulator. That is the copper's way of rusting. iron/steel turns red/brown, copper turns greenish-blue.
 
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To add to above........if you are testing for voltage while the headlights are unplugged from their sockets, you may be leading yourself down a dead end/ forked road

This is because of CURRENT. "Let's say" you have a simple bad connection...anywhere in that path. You turn on the switch, you go out to the lamp connector, and read voltage. You have checked the ground, yet it won't work. The lamp is good, you have checked. WHAT IS WRONG?

Simple........the bad connection "gives up" under the HEAVIER load of the headlamps yet can provide enough "bad connection" for the test lamp to light.

So plug the headlamps back in, let them dangle, then recheck for voltage right at the lamp connector with your lamp.

"I guess?" you have actuall checked the lamps?
 
AJ/FormS said:
If the ground jumper from the battery is properly connected to the core-support, then those other grounds do not affect the headlamp circuit,. But if it's not, THEN the only way back to the battery is thru the firewall to head jumper, thru the engine,to the ground cable, to the Neg. post.
Take a headlight out and jumper the pins to the battery to make sure the dang thing works. If it does then stick it back in and run a ground jumper back to the battery. If it still doesn't work, go back to the bulkhead connector and look for a warm wire; you may have to go all the way back to the dimmer switch light-green supply wire; or the headlamp switch black with tracer supply; or even the #1 splice 12ga black supply from the ammeter guage; or back thru the bulkhead connector still 12ga black,.........
Or just go straight to the bulkhead connector; it's almost always a hi-resistance connection there, or at the headlamp sw itself..
The wire there in question is the big fat 12 ga red from the fusible link,from the battery. On the cabin side this goes to the ammeter, thru it, turns black, and then sneaks off to the #1 splice; then to the headlamp sw then turns green to the dimmer; where it splits into two 16ga wires, a violet and a red , both going out the bulkhead connector again; and then to the headlamps via the sockets. Then thru the filaments to the core support on the headlamp side; thru the core support to the battery via the short usually black jumper sometimes screwed to the engine side of the core support.
If your battery cables are not bonded like the factory cables ,but instead are clamp-on jobber ends, then you may have to disassemble the clamps and clean out the corrosion. The cables are copper and the clamps are supposed to be lead..... which in the presence of moisture, creates a bluish-green compound that can act as an insulator. That is the copper's way of rusting. iron/steel turns red/brown, copper turns greenish-blue.
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Ok all the the core support and battery ground seem to be fine so if I'm understood you right I tried to run a jumper from the light green wire to the battery and came up with nothing it looks like to get to the headlight switch wiring I need to get a little more involved but just making sure I did the first test correctly first
 
Have you tried known good bulbs?
 
RustyRatRod said:
You've SEEN them burn before?
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Yes pluged a wire in the negative side of the socket plug then clamped the other end of the wire to the negative prong on the back of the headlight then I took another wire and ran it from the positive terminal on the battery to one of the positive prongs on the back of the headlight and I lit right up. So it's gotta be something to due with lack of power
 
Justin Angle said:
Yes pluged a wire in the negative side of the socket plug then clamped the other end of the wire to the negative prong on the back of the headlight then I took another wire and ran it from the positive terminal on the battery to one of the positive prongs on the back of the headlight and I lit right up. So it's gotta be something to due with lack of power
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Or ground.
 
Short answer: Get a relay kit from Crackedback or Slantsixdan. Of course that still needs the + signal from the switch to operate the relay.
In the meantime... Did you try both high and low beams? If nothing works its either the ground, or the + side before the switch. I one works and not the other, the problem is in the + side after switch. Check both connectors to see if same. If nothing worked, put the meter neg in the connector neg and check both low and high + side. If you don't get anything, move the neg to the battery. If that works, its in the neg side and you need to work through the circuit till you find where it loses it. If moving neg meter lead doesn't change anything leave it on the battery and work through the + side till you find the voltage. Then move the neg lead back to the headlight connector. Voltage still there? Neg side is good and problem is between where you found + voltage and the connector at headlamp.
 
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Justin Angle said:
I tried to run a jumper from the light green wire to the battery
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If you mean that you jumpered battery positive into that light green wire at the dimmer, and nothing happened then;
either the dimmer is bad
or the bulkhead is not connecting.
orrrrrrrrrrr like said; ground. Cuz you didn't say you took the grounds apart and cleaned them; but only said they "looked good." There are three or four grounds between the headlamp socket and the battery, and "looking good" means nothing, when it comes to electrical..
And I just gotta mention that when the headlamp switch goes, it often takes the fusible link with it.... which may or may not kill the ignition, depending on how badly the link melts. Take the ends of the link, one in each hand and try to give it a stretch. If it stretches obviously it's cooked. But just because it doesn't stretch, doesn't mean it's ok. IIRC the F-link is 7 strands. So even if just one of them is still good, then it will pass the voltage test. But the remaining strand may only support ignition.This is handy to know late at night when you smell melting plastic; just kill the headlights and pray you got at least one good strand left. If the engine stays running, carry on without the headlights.

But if you mean you jumpered the battery Negative to the lightgreen at the dimmer, and you didn't melt the jumper or see sparks,then the break is upstream from the dimmer, and now probably worse.
 
I did take them apart and clean them. Also I did not run a jumper wire from dimmer to battery but rather I ran a jumper wire from that green wire that plugs into the dimmer to the back of the headlight and got nothing however i plugged it into where the black wire that plugs into the back of the ameter and the headlight lit up but I'm not sure if that tells me anything or not. Now should I have a light if I run a jumper from that green wire to the back of the headlight considering that the headlight is grounded? Or am I getting off track?
Thanks for your help. I may just take it to somebody if I still have no luck
 
No , now we are on the same page.
Running power off the back of the ammeter to the headlight and having it light up proves three things; 1) the headlight works, and 2) the ground works, and 3) there is enough electron flow at the ammeter to make it happen. It also proves that all the wiring between the ammeter and the battery is probably ok.
And the problem has to be between the ammeter and the dimmer switch. The red side of the ammeter is the power supply from the battery; The black side is the power going away from the ammeter. So move your jumper to the red terminal and make sure the ammeter is passing juice. All the power for every circuit in the car, has to go thru the ammeter. There is a copper bar in there that is designed to last forever, but the stoopid studs attached to them are easily torn off by aggressive tightening.. so you gotta prove the darn thing is able to pass the juice.
So if that works ,then you are down to just the #1 splice and the headlamp sw.
 
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Swapped out the headlight switch with one from another car and I had headlights again. Thanks for all the replies.
 
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