AkrHack

I have a 67 with one functional parking light. The RH parking light and turn signal works fine. The LH parking light doesn't illuminate and the LH front turn signal is very dim. I unplugged the parking light connector and tested with a volt meter and get a reading of 0 volts. Does this sound like a bad ground? If so, what area should I look for the bad ground connection?

Thanks,
Rick

Nowhere Man

Does the rear singles work? You swap in a known working bulb?

AkrHack

The rear turn signals and taillights now work well. There were some ground issues there as well, but I was able to resolve those earlier today. The bulb in the non operable LH parking light is good. In fact, I bench tested the parking light assembly before I installed it. This verified the wiring and both bulb filaments.

65GGvert

The most common cause is the connector plug going from the socket to the wiring harness. The contacts get corroded and don't allow current to get from the wires to the socket.
The purple wire leaves the headlight switch and passes through the firewall connector and to the driver's side park lamp connector. It ties there and splits off to the passenger side park lamp. So, if the passenger side works, you know the entire circuit is good all the way up to that junction on the driver's side socket. If it's a wiring problem it's in that socket. The black wire off that socket ties to the other grounds at the radiator support. If you jump a wire from the frame to the metal part of the bulb base and the light works, you have a ground issue, either in the socket or connector there, or in the black wire where it goes out to join the others. You could also have corroded or loose contacts where the bulb goes in to make contact. If you have the wrong bulb, it could cause a problem.
When you measured zero volts, where were you measuring? Inside the socket at the contact where the bulb goes? Where did you have the ground wire to the meter connected?

AkrHack

Thanks for your post 65GGvert. It is helping he understand the parking brake circuit a little better. When I got the zero volt reading, I was testing the the female connectors on the LH parking light wiring harness. I'm going back out to the garage and do some more looking around. I'll post what I find a bit later tonight.

AkrHack

I went out in the garage and did some more testing. Here is what I observed with the front parking lights and turn signals. Note that while I was doing all of the testing below the rear taillights, turn signals and brake lights worked properly.

1) When I turn on the parking lights with the headlight switch, here is what happens. The LH parking light is NOT lit and the RH parking light is lit. Oddly, the LH green turn signal indicator on the dash is constantly lit. If I actuate the left turn signal when the parking light switch is on, the LH turn signal flashes normally. If I actuate the right turn signal when the parking light switch is on, the RH turn signal flashes normally and the LH parking light flashes dimly.
2) When I turn off the parking light switch and test the turn signals, here is what happens. If I actuate the left turn signal when the parking light switch is OFF, both the LH and RH parking lights flash dimly. Also, the LH green turn signal indicator on the dash blinks as it should. If I actuate the right turn signal when the parking light switch is OFF, the RH parking light flashes normally and the RH green turn signal indicator on the dash flashes normally.

With all of this strangeness, I'm starting to think that this is more than a bad ground connection.

65GGvert

That would be the exact symptom of a bad ground. It's either in the socket wiring, the connector going to the socket, or the bulb base isn't contacting the ground casing in the socket. Try what I said earlier and run a jumper lead from chassis ground and touch it to the metal part of the bulb base while it's still in the socket and the park lights on. That will bypass all the ground connections to that bulb. The only other possibility I can think of is if the bulb is not inserted properly so the two contacts are shorted by one of the contacts in the socket. (connecting the two filaments together)

AkrHack

It turns out that the issue was with the socket wiring. The parking light that I bench tested stopped working when I manipulated the wiring while routing it under the bumper brace. After I uninstalled that light and hooked it up to a 12v power supply the bulb illuminated. I was then able to make it stop working when I bent the wiring at a 70 degree angle where it enters the back of the socket. Looks like that $20 Bloomington swap meet deal for a parking light with excellent chrome wasn't such a bargain after all!

Thanks to 65GGvert and Nowhere Man for the troubleshooting ideas.