There are a few possibilities that come to mind on this one........ Here’s my best guesses in order of likelihood:
It’s easy to diagnose the ground issue...... connect a digital voltmeter between the alternator bracket (forward outboard corner marked “GND”) and chassis ground lug near the windshield washer bottle on the inside fender. Should not be any voltage difference with the engine running and various electrical loads....... You might see a few millivolts with high current usage, but nothing significant.
Let us know what you find.
Regards,
Mike
I agree with all that mention bad ground -- and Mike's diagnostic technique for an bad ground, specifically engine to chassis ground.
However I don't believe that is where you are have a ground issue otherwise it would effect alternator output and possible cranking speed.
I looked this up a few years back for a fanatic that had a stalling problem when AC was turned on, and driver's side lights acting funny. All which occurred shortly after having a supercharger installed.
The driver's side lights, AC clutch relay and fuel pump relay all ground at G100 (#13 in the diagram) and is shown as located at the bottom left side of engine block.
To check with a meter you would need to BACK PROBE (you CANNOT disconnect the connector) ground wire on one of your lights with one lead of meter and connect the other lead to the alternator ground as Mike mentioned. With the lights on you should read less than about .2 -.5 volts --- anything higher shows you have a bad ground for the lights.
To try and explain what is happening: The circuits are working somewhat by finding an alternative path to ground through the other "shared" ground wires until you try to use those ground wires as an actual ground by turning those circuits on! Example -- fuel pump relay cannot find a ground so some of the electrons travel though the ground wire of the headlight, then thru the headlight filament across the headlight power wire then over to the passenger side headlight and uses its ground while other electrons are doing the same thing though the other lights. This actually provides enough of a ground to energize the relay, UNTIL the power wire has current and the electrons cannot use it to find a ground though the lights on the other side. Now that circuit can't find an alternative path it works in a diminished capacity, if at all. This could also cause a slight glow in the other lights - you might notice the driver's side marker lights have a slight glow to them when turned off with engine running
We call this "Back feeding"
Sorry for the long winded reply - its raining and so I am doing school work from home computer and the teacher side of me kind of took over.
Best of luck and let us know what you find
