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Old 06-29-2016, 09:47 AM
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Strange tail light electrical problem-help please

The drivers side tail/stop light is acting strangely. (the passenger side works fine). All references below are regarding the drivers side tail/stop light.

With the lights off, stepping on the brake pedal results in the stop/brake light illuminating. (as one would expect)

Now, turn on the lights (either parking or headlights), and the tail light illuminate. (as one would expect)

Now step on brake pedal, and on the left (drivers side) tail bezel, the tail light goes out, and the stop/brake light does not go on!!

First I inspected the connector and pins on the tail light assembly. Absolutely no corrosion with connector pigtail and socket in bezel assembly. Busses in bezel assembly are continuous-no problem there. Light bulb, bulb holder, and bulb socket are fine. I lightly sanded all contact point, sprayed contact cleaner on plug and socket.

To eliminate the bezel assembly as a problem, , I removed it and checked the voltages on the plug with a volt meter - The voltages at the plug do show the same behavior as when the tail bezel is plugged in....the tail bezel assembly is not the problem....something up stream is acting funny.

I don't understand how stepping on the brake pedal with the lights off causes the brake light to turn on, but when the lights are on, stepping on the brake pedal results in a) no brake light, and b) turns off the tail light. The two circuits should be isolated......


Help pls!!! Any suggestions???? are appreciated!!!!

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  #2  
Old 06-30-2016, 12:28 AM
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Re: Strange tail light electrical problem-help please

Welcome to the garage.
The problem you described is a well known one on the WJs, eventhough it seems to be a bit different on yours. Brake light ok with no lights on and no brake light when the lights are on, but go out when the brake is used. This is normally a problem of a bad contact between the light fitting and the board. Bending the small copper tabs on the fitting will normally work, or eventually bending the contact strip on the board towards the fitting.
I have never tried to measure the voltage on the connector for this problem, but it seems strange that you loose the voltage to the tail light when pressing the brake pedal.
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Old 06-30-2016, 09:47 AM
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Re: Strange tail light electrical problem-help please

Quote:
Originally Posted by Frango100 View Post
Welcome to the garage.
The problem you described is a well known one on the WJs, eventhough it seems to be a bit different on yours. Brake light ok with no lights on and no brake light when the lights are on, but go out when the brake is used. This is normally a problem of a bad contact between the light fitting and the board. Bending the small copper tabs on the fitting will normally work, or eventually bending the contact strip on the board towards the fitting.
I have never tried to measure the voltage on the connector for this problem, but it seems strange that you loose the voltage to the tail light when pressing the brake pedal.
** Update - Fixed**

Yes, losing the brake light signal seemed strange....So I checked more closely...I had a bad connection to my volt meter. (the alligator clip jumper that I used to attach to the probe had a broken wired in it..grrrrr - cheap Chinese junk....)

After checking the voltages at the tail light socket and verifying that they were the correct values at the correct time (e.g when I turned on the lights and/or pressed the brake pedal), I then swapped in the other tail light bezel...everything worked as it should. This told me that something was wrong with the bezel.

Even thought I checked the continuity of the buses in the non-working bezel, and even bent the contacts on the light bulb holders (plugs), it still was not working.
After some head scratching I noticed that the contacts on the inside of the bezel where the bulb 'plug' goes, was sitting way below the plastic, and could be bent up....they were pushed into the plastic too far that when the bulb plug was inserted and rotated, the contacts on the plug did not touch the mating contact in the bezel....bending them up a little solved the problem.

As an aside, I traced the brake signal back to the brake switch on the brake pedal and found it to be OK.....I had bought a new brake switch just in case I needed it, but did not.

thanks for all the suggestions...
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Old 07-01-2016, 02:45 PM
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Re: Strange tail light electrical problem-help please

Yeh, bad testing equipment can easily ruin your day.
I had the same problem on my jeep a year ago or so and also had to bend the circuit strip out to complete the contact. Problem never returned again.
Good to hear that you have it fixed.
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