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Old 04-08-2012, 01:49 PM   #1
ocala78pacecar
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Default 78 headlights problems

I have read every thread on headlights and either I missed it or did not understand it, so here goes. When I turn on my headlights all 4 lite up, if on low beam, the low beam headlight is bright and the other one is dim, if on high beam, the high beam is brite and the other one is dim. Both sides does this. I have check the switch and it is switching correctly and I have injected voltages at the plug and they do the same thing. Now I have unplug all 4 light and checked the voltages at each plug and I only ready what is suppose to be there (12 volts on low beam and 12 volts on both lite on high beam. Now I am reading these voltages using the ground wire in the plugs of each headlight. I know it has to be a ground issue, but if that is it, why am I not ready different voltages with them unpluged? I have cleaned the ground and get the same thing. I know it is something that I am missing and would appreacate and help. Thanks Norm
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Old 04-08-2012, 04:31 PM   #2
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Old 04-08-2012, 04:38 PM   #3
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You say you've checked the switch and "it is switching correctly" but that would be my first suspect...the switch! But's let's break this down and perhaps some of the wire nuts can figure this out.

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Originally Posted by ocala78pacecar View Post
I have read every thread on headlights and either I missed it or did not understand it, so here goes.
Yeah...most of these have to do with vacuum but good for you for doing your homework.

Quote:
When I turn on my headlights all 4 lite up, if on low beam, the low beam headlight is bright and the other one is dim, if on high beam, the high beam is brite and the other one is dim. Both sides does this.
Does this mean when you write "the other one is dim" are you referring to the same headlamp on the driver's side (or passenger's side) or are you referring to the other low beam (or high beam) headlight goes dim? I think the question is are youisolating both lamps on one side or isolating either low beams or high beams?
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Old 04-08-2012, 05:22 PM   #4
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Thanks for your reply. you are correct when I say dim I am talking about the right and left hand side as a pair (they are both doing the same thing). I have disconnected both sides at less once to see if I could get closer to finding the problem, but no good. I am so have taken the plug off the inside and out side light on each side to see if that would narrow it down, put still get the same results. I going to run a new set of ground wire to one side to see if that help. Thanks Norm
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Old 04-08-2012, 11:56 PM   #5
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I'm not clear from your description what the problem is, but try this.. The outboard lamps have two filaments each, a low beam and a high beam. When you switch from low to high beam, you should see one filament go off, and the other on. Both filaments should never be on at the same time as you will have excessive heat in the lamp, and burn out the filaments or burn the reflective coating off. The inboard lamps have a single filament and should only come on when you are switched to High Beam, at which time the outboard lamps should also be lighted on the high filament. I hope this helps...

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Old 04-09-2012, 02:02 AM   #6
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Pete, I agree, but that is what is not happen. The outboard will switch from one filaments to the other one when I go from low to high beam, but the inboard light filament will be dimmly lite when the outboard light is on low beam and when I go to high beam the inboard light will go to bright and the outboard filament will go from bright to veny dim, almost like a feedback of some type. It has to be some type of grounding issue, but I have disconnected the harness from the high low switch and put 12v down each leg and I still get this result. I am getting a feedback some where, but when I disconnect a plug from one of the light and try and see what the voltage reading is, I always get either 12V or 0V and this is the second set of light that this is doing this on. I am going to disconnect all other light (running and side) from this harness and see if anything changes tomorrow and see if I can find the issue. Thanks for all the help Jerry
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Old 04-09-2012, 04:27 PM   #7
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Quote:
Originally Posted by ocala78pacecar View Post
Pete, I agree, but that is what is not happen. The outboard will switch from one filaments to the other one when I go from low to high beam, but the inboard light filament will be dimmly lite when the outboard light is on low beam and when I go to high beam the inboard light will go to bright and the outboard filament will go from bright to veny dim, almost like a feedback of some type. It has to be some type of grounding issue, but I have disconnected the harness from the high low switch and put 12v down each leg and I still get this result. I am getting a feedback some where, but when I disconnect a plug from one of the light and try and see what the voltage reading is, I always get either 12V or 0V and this is the second set of light that this is doing this on. I am going to disconnect all other light (running and side) from this harness and see if anything changes tomorrow and see if I can find the issue. Thanks for all the help Jerry
It definitely sounds like you have a wiring problem Jerry. You are on the right track trying to isolate it. Either a cross or a missing ground somewhere. Hope you find it soon.


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Old 04-09-2012, 04:55 PM   #8
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Thanks Pete, I had to work on my other issue with the car today Heat and I will findly put a inline cutoff valve to the heat core. My next step on the lighting issue is to unplug all the other lights on the front end, running and side light and see if anything happen. Thanks Jerry
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Old 04-09-2012, 05:02 PM   #9
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It sounds like the dimmer switch. I have replaced a few of these for the same issue, dim lamps, but they were the older style button on the floor.

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Old 04-09-2012, 05:16 PM   #10
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I am not rulling that out, but I would have thought that I would have read some voltage on the plug when that happen and I do not. Not that dose not mean that once I unplug the light that it lost the ground that it was looking for and I was getting a clean read. I just do not like to easter egg these things and would like to get a solided problem before I start ordering $$ parts. Thanks Jerry
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Old 04-09-2012, 05:25 PM   #11
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One of the outboard lamp lowbeam filaments has broken and shorted to the highbeam filament. This will create a voltage path to the Highbeams. Try disconneting the outboard lamp one at a time to find the bad lamp.
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Old 04-09-2012, 05:31 PM   #12
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I have done that. The reason that I replaced them in the first place was that the old lights was doing this and I got new ones to correct the problem and it is still there. Thanks Jerry
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Old 04-09-2012, 05:52 PM   #13
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The headlights have a common ground on the radiator support, have you checked there?
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Old 04-09-2012, 06:45 PM   #14
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Thanks, I have check all the grounds and made sure they are all doing there job. Here is the latest, I took one of the high beam light out and the other side both lights are brighter on low beam and the same on high. Boy does my head hurt. So I remove the plug off of the hight beam on the other side and replace it on the first side and the first side both of the lights are bright on low beam and one bright and one dim on the high beam. I guess I am going to through some money at the dimmer switch. Thanks for you all helps and I will update you later. Thanks Jerry
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Old 04-14-2012, 01:23 PM   #15
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Updated and fixed. I do not like it when someone has a problem and then they findly get it fix you hear nothing, telling people is how you help each other. Now it was either Buba a long time ago or the factory did this wrong or maybe both. I put a new dimmer switch in and had the same problem, at this point I was thinking headlight switch or ground. I when thru all the grounds and redid everyone of them and I still had the same problem. I ran a new ground to the high beam light and again I had the same problem, this is where I when back to my Navy days and did the KISS method. I when back to the online wiring diagram and opened my AIM and took nothing for granted. The first thing was the headlight was in the wrong place, the bright was on the inside and the high/low was on the inside. The next thing that I found was the the ground wire was on the wrong pin on the high/low lights. I had the other set of light that I took out because of this problem, so I took a High/Low light and put power to the high and low side and switch the ground and the high side and did it again and it was pluged wrong. I switch the wires around and low and behold the light work like they were suppose to. I can see where Buba put the light in the wrong position, but to plug them differently, I do not know. The list is getting shorter and the car is looking and driving better. Thanks for all the help and I hope this help someone later on, Jerry
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Old 04-14-2012, 01:23 PM
 
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