Tail light stay on

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sgtcoleman72

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Any one out there know why my tail lights are constantly on. As soon as the battery is connected they will come on. Brake lights, head lights and turn signals all function properly. Just the tail lights think they are special and always want to be on.
Car is a 68 Barracuda
 
Are positive it is the tail lights? Disconnect the brake light switch at the brake pedal to see what happens. Also go to Mymopar.com and download a FSM.
 
One way this could happen is EG a pinched harness that is cross connecting the dome light power to the tail light line. I don't know if all harnesses have the trunk light power in them but that might be as well.

But as usual it is this: WHAT ARE YOU WORKING ON??????

Year make model, and YES!!! That IS!! IMPORTANT!!!
 
Front parked down hill? Mine did that, just the weight of the pedal moved away from the switch enough to light up the brake lights.
Probably just need to adjust the switch.
 
Could be the headlight switch cross shorting
 
67Dart273 said:
One way this could happen is EG a pinched harness that is cross connecting the dome light power to the tail light line. I don't know if all harnesses have the trunk light power in them but that might be as well.

But as usual it is this: WHAT ARE YOU WORKING ON??????

Year make model, and YES!!! That IS!! IMPORTANT!!!
Click to expand...
68 Plymouth Barracuda
 
What electrical work has been done before this started.

What mechanical things have been done before this started



You need to verify that it is the parking lights and not the brake light.


The brake light switch has an adjustment bolt accessable from the pass side of the column
 
Sounds more like brake lights. Barring any electrical shorts, if current was being sent to the taillights, I would think you would likely see the front running lights on also.
 
Eventually you may want to put the original headlight switch back in.
The reason is most replacements have 20 amp circuit breakers instead of the 15 amp breaker it should have.
That is an aside.

In addition to the diagram in the Service Manual, you may find the master tech conference helpful.
For example this one is about reading and using the electrical diagrams.

Lets look at how the circuit is supposed to be, and what is shared and what is not.
L7 is the Rear Tail Light circuit.
1703459089084.png


I beleive you will find the connector for the body harness behind the driver side kick panel.
Circuit L7 is position 3.
1703459242599.png


If you disconnect the halves and the instrament harness side has power, then its onto the next connection.

According to the diagram, the next spot is the headlight switch.
Here it joins with the front parking lamp circuit L17.
1703459472843.png


My guess is there is something wrong with the wiring because if terminal R is hot (has system power) then L17 would also have system power.

Power to the parking lights and tail lights comes to the switch via the B-2 connection. Wire L8.

1703459850089.png


L8 shares a fuse with circuit D31, which feeds both the emergency flasher and goes to the brake light switch.
The fuses fed from the "battery feed" are always hot when the battery is connected.

Seems like you are looking for a cross wire short, an incorrectly connected terminal, or as earlier suggested brake/turn circuit.

If you find its a terminal, they can be removed from the plastic hosuing using a cotter pin, a hairpin, or actual proper tool.
 
Mattax said:
terminal, they can be removed from the plastic hosuing using a cotter pin, a hairpin, or actual proper tool.
Click to expand...
To remove the covers, depress the terminal's retaining barb. There's a little cutout in the plastic to slip a tool in.

upload_2018-12-27_22-47-31-png.png




factoryterminal01-gif-gif-gif-gif.gif



Then the terminal can be slid out the back.
 
Mattax said:
Eventually you may want to put the original headlight switch back in.
The reason is most replacements have 20 amp circuit breakers instead of the 15 amp breaker it should have.
That is an aside.

In addition to the diagram in the Service Manual, you may find the master tech conference helpful.
For example this one is about reading and using the electrical diagrams.
[/URL][/URL]

Lets look at how the circuit is supposed to be, and what is shared and what is not.
L7 is the Rear Tail Light circuit.
View attachment 1716182685

I beleive you will find the connector for the body harness behind the driver side kick panel.
Circuit L7 is position 3.
View attachment 1716182686

If you disconnect the halves and the instrament harness side has power, then its onto the next connection.

According to the diagram, the next spot is the headlight switch.
Here it joins with the front parking lamp circuit L17.
View attachment 1716182689

My guess is there is something wrong with the wiring because if terminal R is hot (has system power) then L17 would also have system power.

Power to the parking lights and tail lights comes to the switch via the B-2 connection. Wire L8.

View attachment 1716182693

L8 shares a fuse with circuit D31, which feeds both the emergency flasher and goes to the brake light switch.
The fuses fed from the "battery feed" are always hot when the battery is connected.

Seems like you are looking for a cross wire short, an incorrectly connected terminal, or as earlier suggested brake/turn circuit.

If you find its a terminal, they can be removed from the plastic hosuing using a cotter pin, a hairpin, or actual proper tool.
Click to expand...

Mattax said:
Eventually you may want to put the original headlight switch back in.
The reason is most replacements have 20 amp circuit breakers instead of the 15 amp breaker it should have.
That is an aside.

In addition to the diagram in the Service Manual, you may find the master tech conference helpful.
For example this one is about reading and using the electrical diagrams.
[/URL]

Lets look at how the circuit is supposed to be, and what is shared and what is not.
L7 is the Rear Tail Light circuit.
View attachment 1716182685

I beleive you will find the connector for the body harness behind the driver side kick panel.
Circuit L7 is position 3.
View attachment 1716182686

If you disconnect the halves and the instrament harness side has power, then its onto the next connection.

According to the diagram, the next spot is the headlight switch.
Here it joins with the front parking lamp circuit L17.
View attachment 1716182689

My guess is there is something wrong with the wiring because if terminal R is hot (has system power) then L17 would also have system power.

Power to the parking lights and tail lights comes to the switch via the B-2 connection. Wire L8.

View attachment 1716182693

L8 shares a fuse with circuit D31, which feeds both the emergency flasher and goes to the brake light switch.
The fuses fed from the "battery feed" are always hot when the battery is connected.

Seems like you are looking for a cross wire short, an incorrectly connected terminal, or as earlier suggested brake/turn circuit.

If you find its a terminal, they can be removed from the plastic hosuing using a cotter pin, a hairpin, or actual proper tool.
Click to expand...
Fun with electrical continues. I do have power to L17, with both fuses pulled out. Disconnecting the terminal behind the kick panel panel turns the lights off. I'm gonna pull the fuse box out and see what's going on behind
 
Interesting but the connection to the parking lights not obvious.
X1 labelled "cigar lighter" overheated and the Dome light feed is missing?
or the other way around.

PS.
The colored pdf version of the FSM diagrams is in this post.
www.forabodiesonly.com

Colored schematics 67 barracuda

Hi all wondering if anyone has or has seen colored schematic for 67 barracuda. I found one for 69 but can't find 67. I checked mymopar.com already. Thanks Steve
www.forabodiesonly.com www.forabodiesonly.com
 
Looking at the diagram, cigar lighter only goes directly to cigar lighter, and Dome light feed goes directly to the connector behind the kick panel.

Does the dome light work? Or more to the point, was it getting power?

Know that the dome and related lights work by having a hot connection all the time. Circuit is completed when any one of several switches on the return wire is closed. (Switches are in the door jamb and in the headlight switch).
 
This may help a with respect to the harness routing and support.
1703595292482.png

1968 models are "D" Series
 

Mattax said:
Looking at the diagram, cigar lighter only goes directly to cigar lighter, and Dome light feed goes directly to the connector behind the kick panel.

Does the dome light work? Or more to the point, was it getting power?

Know that the dome and related lights work by having a hot connection all the time. Circuit is completed when any one of several switches on the return wire is closed. (Switches are in the door jamb and in the headlight switch).
Click to expand...
No
Mattax said:
Looking at the diagram, cigar lighter only goes directly to cigar lighter, and Dome light feed goes directly to the connector behind the kick panel.

Does the dome light work? Or more to the point, was it getting power?

Know that the dome and related lights work by having a hot connection all the time. Circuit is completed when any one of several switches on the return wire is closed. (Switches are in the door jamb and in the headlight switch).
Click to expand...
No power to the dome light. Another question thou. The rubber seal around the tail housing is deteriorated. When I remove the bulb from the housing it shuts off that side. Is it supposed to be grounded through the light housing?
 
Your in good hands with @Mattax

Some things I noticed on your fuse block...


Red - might be debris but looks like melted wire
Blue - Obvious melted wire
Yellow - the sheathing has that bumpy look of once almost melted wire
Screenshot_20231226-101028.png



One of the issues with melted wires is they can get melted together inside the tape wrap and you don't see it unless you take the tape wrap off.

Not saying you should do that just mentioning it
 
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sgtcoleman72 said:
No

No power to the dome light. Another question thou. The rubber seal around the tail housing is deteriorated. When I remove the bulb from the housing it shuts off that side. Is it supposed to be grounded through the light housing?
Click to expand...
I do not understand what you are saying here. I mean, if you remove the bulb, of course it is shut off.

EG: My 70 RR the sockets had 3 wires, so there was a dedicated ground to the socket shell. I don't know if your Barracuda would or not.

But I think we have strayed. I would concentrate on the problem first. "Where" is the tail lights getting power when they should not?

1....Disconnect headlight switch. If the power stays on, then it is not coming from the light switch

2....With the problem "showing," access the kick panel rear harness connector. Look up the wire colors, and probe all pins of the connector. With brake lights off, and key off, there should be only 1 or 2 pins active. The tail lights (because of the problem) and the dome light circuit if it works. If you can pull the fuse for the dome light circuit, that should kill the tail lights IF it somehow crossing wires in the harness.

If so, verify by pulling both bulbs, separating the kick panel harness, and then check continuity. The tail light wire should NOT show continuity to any other wire in the harness, or to ground.

If it does, the problem has to be right there in the rear harness

3..If 1 or 2 brings no answers, there is not much left. The path from the kick panel connector, at the tail light circuit, up to the headlight switch, is a short length of wire. There should be nothing else on that. If it is still getting power, trace the harness from the kick panel to the light switch.
 
sgtcoleman72 said:
No power to the dome light. Another question thou. The rubber seal around the tail housing is deteriorated. When I remove the bulb from the housing it shuts off that side. Is it supposed to be grounded through the light housing?
Click to expand...
68 Taillights are different than my current 67.
However, the upside down Christmas tree symbol is ground. So each lamp is grounded to the body directly. No wire.
1703615376948.png


While grounding can be an issue, the problem at hand is on the feed side.

Let's go over the findings:
Power in L17 and and L7 with the switch off. But only the rear lights are on.
Do parking lights work with switch on?
Do the rear lights turn on with the connector (or just the one terminal) removed from the headlight connector?

Dome light fuse is missing one and has one damaged wire.
Dome light doesn't work.

Personally I might do a little more testing for hot, for example in the front parking circuit and in the dome light circuit.
This would be to try to determine which circuit and location areas could be a cross wire short.
edit: The steps in the above post are very clear and I suggest you follow them

At some point you will need to address the fuse box. Disconnect the battery and seperate or partially seperate the fusebox from the harness.
The terminals on the feed side slip off. If you have to do the circuits out (other side) will require removing the fuses and releasing the fuse holder clips.

Look at the power feed to the box (Red with tracer) for pinching or contact to the L17 and also the other wires.
 
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