8 cylinder front engine iconic vehicle
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By ChrisZ
So the other day I noticed my left (passenger) headlight was putting out a lot less light than the other one. Figuring it was a ground issue I put it on the list of things to do.

This weekend I checked it out and sure enough only about 6 volts across the lamp and when I use my meter in amp mode between the brown ground wire at the lamp and a solid ground (the plate holding the diagnostic port on the front of the engine) I got 2.1 amps and the light went to bright.

Odd thing is the other lights on that side are not dim, if the ground was bad I'd expect them all to either be bad or improve when I jumpered the ground to ground. Nope.

Tried loosening, then tightening the ground point with some deoxit spray to boot. Which of course can only be accessed from under the car with a very long 10mm wrench and moves a tiny bit due to the AC dryer being in the way. But no improvement at all. Checked the fuses, all good so I just grabbed some #14 wire, ran a temporary line from the light to the bracket that holds the condenser to the rest of the car. Light now bright, I'll work on it more in the spring.

Question: Is there enough slack in those ground wires to get them cleaned with sandpaper or a bristle brush or should I plan to take off the bumper or at least the AC condenser?

Meantime all is still not quite right: The passenger driving light (the one next to the fog light) was also doing something odd: It was on when the headlights were on but if you turn the lights to parking light mode the passenger driving and front marker lights both seem to go off while the driver's side is on. Turn the headlight on and all is well. Foglights come on regardless and are the same brightness side to side.

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By Hey_Allen
At first glance, it sounds to me like one of the lights has is ground floating and is using the headlight as it's ground path.
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By Mrmerlin
check the wire connections at the junction blocks also you could have a broken wire at the metal harness clamp under the headlight pod the harness flexes and the wires break inside.
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By ChrisZ
Hey_Allen wrote: Sat Jan 22, 2022 6:44 pm At first glance, it sounds to me like one of the lights has is ground floating and is using the headlight as it's ground path.
Yeah, it is a bit odd. Could be something in the relay as well, but I don't think that controls the grounds. I'll put the car up on ramps and take a long look at the ground point as soon as it warms up.

I also think I have a spare headlight relay system, will try popping that in to see if it fixes the running light issue.


Thank you for all the feedback. @maddog2020 I […]

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