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Discussion Starter #1
OK, my first post to this forum and probably many more. I recently purchased a 67 ss396 L34 and did not check the headlights. When I turn on the lights the fuel gauge turns off, right blinker light comes on, and alternator light glows dimly. I think this is a ground problem or could be the switch. I haven't tried to find it yet but would like to drive at night some time. Any thoughts how to start on this?
 

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Not seeing a quick answer at the moment. I assume this is occurring with the engine off but the key to the ON position. Almost looks like 2 things are wrong. First thing I would try is to remove the large connector off the voltage regulator. Do this with the engine off. Pull the headlights on again. That should stop the GEN light from coming on. On that connector there is a brown wire. With the connector off the regulator, measure the brown wire to ground (key ON, engine off). You should have about 12 volts. If you do, does the fuel gage still turn off? This is one way to check the power line to the fuel gage. Post back with the findings.
 

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Sounds like a ground problem to me. Make sure there's a seperate ground of the negative battery cable to the front fender and make sure it's clean and tight. Make sure you have ground straps from the engine to the firewall. Also check the grounds in the trunk for the rear lights and the fuel guage. Make sure your radiator support is properly grounded as well as your headlights and parking lights. More often than not, some of the most seemingly complicated problems have a simple solution. Good luck.
 

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Discussion Starter #4
OK, since car is in my warehouse I checked John on my way home tonight as you suggested. Removing the connector on the voltage regulator did put out the Gen light. Interesting observations with the key on and headlight switch on. I did check the brown wire and it is slightly over 11 volts on all these tests. With the dash dimmer control off & on low beams on, the gauge is good. Low beam headlights are on but right slightly dimmer than left. Had a bad left rear bulb but it is hot & right rear is on - actually rears are fine. Slowly turning dimmer on the gauge drops to 1/4 & red high beam indicator starts to glow. Turning high beams on the right low headlight beam is now out and left front is dimmer than on just low beams, high beams are good and strong. With the dimmer off, the gauge goes to about 1/4, the high beam indicator light is on, slowly turning the dimmer on, the beam light goes out, the right turn indicator comes on, and the gauge drops to below 0. The lights on the heat/air fan contol panel all work with the dimmer control as well as the dome light when it is all the way over. Any suggestions what to check now?
 

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It's the affect on the fuel gage I am looking at in all of this. The brown line I asked you to measure is tied to the fuel gage pink wire through the GEN lamp. It stayed high (about 12 volts) and that's what it should have done.
The fuel gage, on that year, has 2 wires on its connector. A tan one and a pink one. We already know that the pink one is OK. Leave the connector off the regulator for the moment.
As Paul suggested: You do have a small ground strap from the negative battery post to the inside right fender? If yes.
The fuel gage gets its ground through the fuel gage frame. Attach a wire under one of its mounting screws. Attach the other end to a good ground somewhere under the dash. Try your tests again and see if the gage still moves around.



[This message has been edited by John_Muha (edited 02-08-2002).]
 

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Just wanted to show how the 66/67 instrument cluster is grounded. The ground strap is under the mounting screws just above and to the left of the steering column. I included an unattached strap so that you can tell what it looks like. As can be seen the one on the cluster has rust and may not be a good ground.


click for pic

[This message has been edited by Elree Colby (edited 02-09-2002).]
 

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Great picture Elree and you already figured I would be asking you where the strap was. Was't the high side of the meter, had to be the low end.
 

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Discussion Starter #8
Thanks for the replys and I will head over to work on the car shortly. I will check on the dash and gauge grounds and report back tonight. I do recall seeing a ground wire off the negative battery post but thought it went to the radiator frame or headlight area, will double check that. I also recall seeing a ground strap from the fender well to the frame by the battery.
 

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Wow-this forum was right on and saved me a lot of work. Checked for the instrument ground strap and could really find nothing.After some contortions I looked to the left of steering column and saw no extra grounds. I put a ground wire under the bottom fuel gauge mounting screw and attached the other end to one the steering column mounting bolts...it all worked. I made an error in my previous comment about the battery ground,it is indeed grounded to the fender well, the other wire to the front was off the positive post. In checking the headlights I did still see that the right headlight low beam goes off when I turn on the high beams. The previous owner put in halogen high beams and the low beam is a philllips. Are there two filaments in the low beam and perhaps one is broke?

Of course, I still have 3 other electrical projects on this car - 1) radio does not turn on, saw a cut black wire coming out of the back of the radio and it may just not be grounded. Ran out of time to try that. 2) Horn does not work, in fact it has just one of the two and I will either get a repro or check ebay but also need to check the circuitry. 3) The brake light switch at the pedal, this is a 4-speed, is loose and I was told that the brake lights work but also come on sporadically while I am driving. It looks like the switch threads into the framework above the pedal and it has been stripped since it is very loose and was just cable tied to keep it on there.
Your other suggestions were right on and would appreciate any more you may have.
 

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You're getting there. When I had you add the jumper to the fuel gage it was only meant as a test. It was to provide a known good ground to the meter and not rely on anything else. Elree Colby showed you where the real dash ground is. To fix it properly, you need to fix the area Elree showed you.
If a headlight has 3 wires on it, it has 2 filaments. Two wires on it, it has 1 filament. Take a peek.
Post your other problems one at a time when you are ready to work on those. Easier on everybody. Keeps the questions and answers together. The bill is in the mail (j/k).
 

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Discussion Starter #11
Thanks again John,Paul& Elree, will set up proper ground to dash. Will post other questions as new topics after I first try to solve the other electrical problems mentioned since most are a little simpler than this ground was and I know where to start, maybe.
 

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I have a 68 chevelle with 6 cylinder and have the same problem,,lites turned on and gas guage goes to empty, four way flashers lite in dash come on, also happens when wiper switch is on. Is the instrument ground on this car the same place as on the 67 mentioned above?

thanks,

bob
 
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