Tail light stays on

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nakabrd

nakabrd

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I have a '71 Dart Demon. The left tail light stays on all the time. The other lights work as they should. Can anyone give me an idea what the problem is? Thanks
 
nakabrd said:
I have a '71 Dart Demon. The left tail light stays on all the time. The other lights work as they should. Can anyone give me an idea what the problem is? Thanks
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I would start by grounding that light socket to a good ground.
Temporarily touch a wire to the socket right at the bulb and to the bumper or body metal.
These cars are notorious for back feeding power because of bad grounds.

Then pull the drivers kick panel and make sure it doesn't have a short between the trunk light wire (always hot) and the tail light wiring, (they share the same connector) and then if that isn't it work my way forward up under the dash following the tail light wires till I found where that tail light wire was crossed with power.

A 12v test light works well for this.
 
"All the time?" You mean when parked with all other power off? What do you do to keep the battery from going dead?

If the above is true, part of the harness must be crossed/ shorted to something live. The only thing in the rear harness that would be live is the feed for the trunk lamp

If so, pull the rear seat and look for a pinch in the harness. If not, pull the carpet/ left kick panel until you can access the harness and inspect it. There's a connector in the left kick panel to separate the rear harness. Separate that and probe that connector to see if power is being fed to the tail circuit from somewhere "ahead."

You can download wiring diagrams and service manuals from MyMopar. some of the manuals over there came from the guys right here, including TB
 
Thanks for the replies.
Dana67 - I just purchased the car and I'm trying to troubleshoot problems. Ihaven't done anything to the car yet.
67Dart273 - I pull the bulb to keep the battery from draining.

More info - If I turn the headlights on, the left tail light (the one that stays on) goes out. Turn off the headlights and it comes back on. Same with the blinker, turn on the left blinker and the light turns off and it blinks as it should. Turn off the blinker and the light stays on. Thanks for the help.
 
nakabrd said:
Thanks for the replies.
Dana67 - I just purchased the car and I'm trying to troubleshoot problems. Ihaven't done anything to the car yet.
67Dart273 - I pull the bulb to keep the battery from draining.

More info - If I turn the headlights on, the left tail light (the one that stays on) goes out. Turn off the headlights and it comes back on. Same with the blinker, turn on the left blinker and the light turns off and it blinks as it should. Turn off the blinker and the light stays on. Thanks for the help.
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This is a classic ground issue symptom.
 
Thanks Trailbeast. It may sound like a classic ground issue but when I ground it with a wire, the bulb gets brighter (like going from tail lights to brake lights). The green wire going to the socket is powered 100% of the time, thats why it's on all the time. I disconnected the harness at the driver kick panel and the green wire is powered going back under the dash. I'm guessing it is contacting a hot wire under the dash somewhere. Does this sound reasonable?
 
nakabrd said:
Thanks Trailbeast. It may sound like a classic ground issue but when I ground it with a wire, the bulb gets brighter (like going from tail lights to brake lights). The green wire going to the socket is powered 100% of the time, thats why it's on all the time. I disconnected the harness at the driver kick panel and the green wire is powered going back under the dash. I'm guessing it is contacting a hot wire under the dash somewhere. Does this sound reasonable?
Click to expand...

Yep, sounds reasonable to me.
And we also know there is a ground issue at that socket.
The light shouldn't change at all when you ground the socket.
Unplug your headlight switch connector and see if the light goes out, and if it does the problem is likely in the headlight switch. hint (which always has power)
 
Find out what circuit powers it. Pull the fuses one at a time. Maybe it's a bad light switch. Unplug the switch. Examine the diagram to see what in the car is "hot" at all times Brake circuit, trunk light, dome light, cigarette lighter etc. There are not that many fuses. It would not be long I'd have the cluster out and or the seats out to examine under the dash. Look for suspicious parts of the harness
 
Green wire would be left turn. Hazard switch is built on the turn signal switch and it has a hot at all times. Good hunting
 
RedFish said:
Green wire would be left turn. Hazard switch is built on the turn signal switch and it has a hot at all times. Good hunting
Click to expand...

Which would also explain why his light gets brighter when he grounds it.
(because it's actually a brake/signal light and not a tail light)
This means it could even be a brake light switch adjustment but the other side doesn't light. (another possible ground issue)
 
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