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Rear tail light assembly malfunctioning - SOLVED


Ensign
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I have a ’72 tii

The left/rear taillight assembly is malfunctioning:

1.        When the left blinker is engaged, the blinker AND tail light flash.

2.        When the light switch is turned on, the tail light AND blinker-light are on steady.

3.        With the light switch on, the left blinkers do not work.

The right/rear tail light assembly works properly in all modes.

The wiring at the tail light assembly is correct with regard to the wiring color codes and does not look tampered with.

It would seem that circuits for the left/rear tail light and left/rear blinker are connected somewhere.

Any ideas on where I should concentrate my search.

I found a couple of older threads describing a similar issue, but with no solution.

Thanks, as always, for your time.

Tony

Edited by Ensign
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And make sure the spring clips that engage the center bulb contact aren't touch each other.  As these assemblies age, the plastic that holds the contacts gets worn, and allows the clips to move sideways.  On a roundie light assembly, some are very close together; if they touch, you're gonna get both bulbs lighting at the same time even if only one circuit is engaged.  Same with the push-on terminals--they can lose their insulators and without 'em it's easy for them to touch each other

 

Let us know whatcha find...

 

mike

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Thanks for the responses.

The bulbs are new, the light assembly is clean and I ran a separate ground.......still no luck.

I disconnected the left/front parking/blinker light thinking that the problem could be there since the two circuits involved run to a single bulb, but I got the same results.

I also checked the left/front parking/blinker bulb and with the parking lights on, both filaments are lit, so the front and rear lights have the same symptoms.

I may try disconnecting the 4 circuits from the fuse box, one at a time, in an attempt to isolate the problem as front vs. rear and parking vs. blinker.

ughh.

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I hate chasing electrical gremblins :(

 

A few ideas to try:

 

1.  Activate your emergency flasher.  See how the various lights interact.

2.  Swap out your flasher with a different one.  See if that makes any differences.

3.  Apply no-ox-id or equivalent to all your contact and ground points.

4.  By chance, did you recently swap out some of the incandescent bulbs to LEDs?  That may cause incompatibility problems with the flasher.

5.  By chance, are the two wires in the left front signal lights swapped?  One should be for the blinker, the other is for indicator/running light.

 

Good luck,

 

 

Trieu

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So, I wanted to wrap this up. I spent days studying the wiring diagram, tracing wires and making pages and pages of notes. Unfortunately none of this helped, as the wiring and fuse panel appeared to be intact and correct, but I did solve the problem.

I hadn’t noticed it at first, but the left/front parking and turn signal light had the same symptoms as the left rear taillight. The parking light would come on with the blinker and the blinker would come on with parking light. I did run new ground wires to the front parking lights, but that made no difference.  I also swapped out the hazard switch, the flasher unit and light bulbs. I removed the radio and cut out all the spliced-in wires that have been added over the years. The problem persisted.

I have an extra turn signal stalk, so just for the heck of it I plugged it in to the 9-pin receptacle, and just like that, the problem went away. The difference between the two turn signals stalks is that the existing one has all 9-pins in the plug, while the extra one does not have the center pin. I did some researching and found that a new, correct turn signal stalk also did not have the center pin. I assumed the existing turn signal stalk was wired differently and that was my problem.

I proceeded to remove the steering wheel and the column pads to swap out the switches. As I removed the bottom pad, the buzzer contact fell out, hanging by the wires. I looked at it and wondered if this metal-cased thing floating around in there was making contact with the exposed solder points on the switch and causing the problem. So before removing it, I plugged the existing stalk back in and, to my surprise, the lights worked perfectly.

That’s it. There may be a lesson in there somewhere, but I don’t know what it is.

Tony

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