I am trying to track down pretty much the last electrical issue I have with the car. It is an odd one. The symptoms:

1) Car runs and drives fine, all turn signal work when told to. All brake lights work as supposed to. All running lights work when switch is in running light position. Headlights work, low and high.

2) Headlight switch in off position, doors closed and courtesy lights off, the rear tail lights and arrows are on, and brightness adjustable via the headlight switch.

3) Oddest one. Headlights on, car starts and runs fine. Try and turn off the car with the key, and it will not shut off. I can completely remove the key and the engine will stay running. Turn off the headlights and the engine shuts off.

New engine, front and rear light harnesses.

I had a similar problem when I installed my MSD box. They supply a diode you have to install off the voltage regulator. Otherwise the engine would stay running. Sounds like you have some current flowing where it shouldn't be.

Oh, I'm sure I have some current in the system coming from somewhere. That is what I am trying to find. This issue was in existence before I installed the Pertronix III and was a factory points system.

Weird. Only thing I can suggest is that power is still being supplied to the ignition through the headlamp circuit. That's where you should start. There has to be some wiring issue.

how about the ignition switch?

That is kinda cool problem. I would look at the ignition switch too.

Was this a modified harness for HEI? Take the power line to the coil and measure it to ground, with and without the lights on and see if it a full 12volts or just a partial. In any case you should have no voltage on that line.

It sounds like a bad ground. When you shut off the key with the headlights on, there's voltage to the ground side of the coil, reversing its polarity. Coils still work with the polarity reversed, but if you try to put any load on it there won't be enough charge to get really good spark.

Look for a bad ground in your lights circuit.

I agree, check for grounding. Also, I would agree that you should swap out the ignition to be sure that's not it. Has the harness to the ignition been modified? I put in a kill switch, perhaps you have had your harness jumped and rewired poorly. Is the engine grounded in 2 places and then I think there is a frame to body ground. Your battery is grounded to the fender and the RH head?

One other thing to try is unplug the headlights and leave switch on.. Ie. Is it coming back from bulbs or just switch.

All wires to the coil are in good shape and connected properly?

I have already replaced the ignition switch, headlight switch, turn signal switch, wiper motor switch and door jamb switches...

New harnesses, except for under dash. No apparent splices.

Engine grounded in 3 places. block to body, block to frame, block to frame to body. Battery ground to block and to pass fender. I too suspect a bad ground somewhere as it would also explain the rear running lights being able to be on when the light switch is in the off position, but by turning the dimmer they come on. The fronts do not.

I will have to check for bad ground for the lighting circuit. Any particular place recommended to start. Off the top of my head, I'm not sure where the specific ground wire for the lighting circuits are. I know most are picked up via the socket holders.

Could a bad printed circuit board cause such a problem? My ammeter does not work and I purchased one to see if that remedies that problem. Just have not gotten to that yet.

Thanks for the feedback so far.

The front headlamp harness grounds in two places on either side of the radiator support. When I had my front end apart I placed an additional ground strap from the horn relay attachment bolt to the frame rail just for good measure. Whether it was necessary or not, who knows. But it makes me feel warm and fuzzy

Do you know of another FB in the area that you can compare with? Also have a nother set of eyes look at it.
Your grounded at the trunk as well? Might have to review the electrical systematics to better understand what's going on.

We need to isolate where the power is coming from (failed circuit).
If the car is on, headlights are on then turn off ignition car & lights stay on. At this point try this:

Unplug each headlight starting from LH to RH side to see if engine quits.

If the car quits you probably found the circuit problem.

Also, how are you front signal lights doing. They are buggers to keep grounded. Ground them with a wire clipped to the frame to be sure they are grounded.

Front turn signals work properly, both running and turn function.

I will need to set aside some time this weekend. I think your idea of disconnecting the lights one at time is a good starting place. I do not think it is in the front of the car though as I recall completely disconnecting the front light harness and still had the rear arrowhead issue. This was prior to discovering the not being able to turn off problem though. I think the two issues are related.

As for trunk grounding, I do not recall having any specific ground wire attached anywhere. I do have the pointed metal ground bars on each of the arrowhead indicators. I thought originally that may have been the issue so I ordered them.

I was under the impression that if the lights did not have a good ground, they would not work anyway. All lights work, just not as intended. As I mentioned before the rear arrowheads work when they should. However, they ALSO work when they should not, when the light switch is in the off position and the dimmer switch is turned to the on position. They are even dim-able this way. The ignition does need to be in the on position for this to happen.

The reason we ground the circuit at the lights is to control where the circuit completes. If it does not ground there it will find a way to do it by going back thru another wire if it has to. The reason we have ground rods for buildings is to motivate where the electricity from a lightning strike goes to get to ground so it does not go thru other devices in the home.

My wire is out of car right now so i had a look.

Each headlight pair has a ground wire. There is also a ground wire near the coil, and a ground wire near the regulator.
The clearance lights in rear are ground thru it of it's frames so make sure the light frames are grounded. The front signal lights are grounded thru it's frame as well.

click on:

I'd check for continuity between the headlite switch (plug off the switch) and the coil +, with the ignition on/off, then with the bulbs unhooked..., fuse out etc... at some point you will be able to narrow down the run....

Electrical tracing is {fun} . Kind of like detective work, with the wiring diagram the rap sheet LOL.

By that reasoning, I should probably look elsewhere from the actual lighting circuit for the 12v source.

Here is my thought. If I can get only the dash and arrow head lights to turn on via the rheostat portion of the light switch, with it in the off position (all the way in), power must be feeding from elsewhere. (Unless the rheostat also controls the interior courtesy lights when the light switch is in the off position, I can't remember if it does.)

Does this possible scenario make sense... My ammeter used to work. It does not now. It has a light in it. Power is fed to it via the printed circuit board. If it is bad, it might feed back through the light into the rheostat and cause the arrowhead light issue. Additionally, when the lights are in the on position, power may feed back into the ignition system since the ammeter is part of that system anyway.

Maybe?

I still think you should run this test of pulling the positive wire off the coil and testing for full +12 volts with lights on/off. If you don't have voltage on the line, I would be more inclined to agree that its a grounding issue. If you do have full or partial voltage on the + side wire of the coil start chasing it back.

If you have the yellow line on the coil that is an easy check to pull that off and see if that is playing a role. I wouldn't think it is as it has nothing to do with the light switch. But check it anyway.

Then your down to just tracing out the pink wire under the dash. Your main red power comes into the car feeding the light switch, ignition and fuse box. The ignition feeds the pink wire that goes out to the coil but is also shared by the Gauges, reverse lights and a few other things.

As for the Amp meter its a stand alone gauge that doesn't have a ground reference that I recall. Just two 12volt sources from different locations that would cause a small trickle of current. I still need to trace that my self.

I don't think that can be the source of the issue. I have had this problem prior to me switching the power to the coil from the factory resistor wire to a direct 12 volt from the open acc post on the fuse panel when I switched from points to Pertronix III.

EDIT: Wait, you are saying check on the OTHER side of the coil for power? The yellow wire is attached to a terminal along with the pink/black wire and cannot be separated without damaging the harness.

Check the POLARITY of the voltage at the coil with a good DMM with the key ON and the key OFF but with the lights on. I suspect that the polarity will be reversed and the voltage relatively low with the key off but the lights on.

Ignition off, lights off 0.0V
Ignition on, lights off +12.1V
Ignition on, lights on, +11.9V
Ignition off, lights on, +10.9V

Definitely not the direction I was originally heading. Time to break out a wiring digram!

Now we are getting some where. So your pink/yellow are tied together, so what I would do is dissconnect the yellow from the starter solinoid. This should have absolutly nothing to do with it but then again you shouldn't have any voltage at that point with the key off and lights on.

Do you have the colored wiring diagram PDF that fits on one 11x17 sheet of paper? If not send me your email address and I will send it to you.

With your ignition off and lights on and your volt meter set up to watch for changes I would start to disconect things under the dash untill your voltage drops to 0. disconnect the ignition, disconnect the gauge pluge, disconnect the light switch, disconect your reverse light switch at the shifter. Something is back feeding your pink wire under the dash, and that pink wire feeds a lot items under the dash.

Pull fuses one at a time until you have 0 volts at coil + with light switch on, ignition off. That won't test all circuits, but it will eliminate a lot of possibilities. If none make a difference you'll still need to continue to underdash connectors, but fuses are an easy place to start. Also pull anything tapped into the IGN or BAT tap on the fuse box, if it is connected to another source it will back feed.

Have you had the steering column apart? I had some very weird things going on like that when I took my turn signal switch out and back in. I had the wires routed incorrectly through the bowl and they were being pinched when tightened. It created a ground/power loop somehow and my turn signals ended up causing the headlights and interior lights to flash.

I have had the steering column apart a number of times for various reasons. This problem predates those times. Thanks.

I will start by narrowing down the circuit via Vikki's suggestion as soon as I get some time. Hopefully this weekend, but family obligations are taking up a lot of spare time right now.

Thanks for all the suggestions.

The engine compartment side of the bulkhead connector splits in two when it's unbolted from the firewall. One half has the lighting circuits on it . The other half has the engine and gauge related circuits. Unplug your bulkhead connector and plug the engine circuits back in with the lighting circuits still disconnected. Check to see whether everything but the lights still function.