1994 Jeep Wrangler tail lights

Tiny
SCOTTPAFF
  • MEMBER
  • 1994 JEEP WRANGLER
  • 2.5L
  • 4 CYL
  • 4WD
  • MANUAL
  • 190,000 MILES
My tail lights work until I turn the headlights on. Then I get nothing in the rear. No brake lights or blinkers. Is this a light switch? Am I in the right direction.
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Monday, September 1st, 2014 AT 6:49 PM

6 Replies

Tiny
CARADIODOC
  • EXPERT
Nope, you have a broken ground wire. To prove it to yourself, look closely at those tail lights and you'll see both filaments, the tail light AND the brake light are glowing. If you remove the right rear bulb, the front ones, and possibly the side marker lights, the left rear one won't work at all.

Given the type of vehicle, it likely has a trailer wiring harness. That's the place to start looking. If someone spliced in that harness with Scotch-Lok connectors, you can bet the wires are corroded apart. Those connectors are used all the time but must never be used outside because they don't seal out moisture.
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Monday, September 1st, 2014 AT 8:15 PM
Tiny
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Thanks Ill check that first. I didnt think about that. Smart help.
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Monday, September 1st, 2014 AT 9:52 PM
Tiny
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If I check with a test light and they all give power to the left? I'm fine from the light swtihch, is that right?
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Tuesday, September 2nd, 2014 AT 12:22 AM
Tiny
CARADIODOC
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You have tail lights, so you know there's voltage getting to the bulbs. A test light will show the same thing. If you want to prove to yourself there's a bad ground, use the test light with its ground lead clipped to a metal part of the body or frame, then touch the probe to the ground wire for the tail light bulb. You'll find the tail light gets brighter and the test light glows but not full brightness.
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Tuesday, September 2nd, 2014 AT 7:24 PM
Tiny
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I got the ground. Now when I turn the lights on the tail lights work. The brake lights work fine. The blinker will blink once and then that is it. If I use the blinker switch manually they work with the lights on. The blinker lights work fine until the head lights are on. Is this still a ground problem or could it be something with the blinker that goes in the fuse box?
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Monday, September 8th, 2014 AT 7:26 PM
Tiny
CARADIODOC
  • EXPERT
The flasher has a little heating element inside. It doesn't get hot enough to flash when there isn't enough current flow. That is caused by that bad ground or not all the lights are working. If you have one light in each corner of the vehicle, you need a flasher made to operate two bulbs. If there's two bulbs in each rear corner, you need a heavy duty flasher made for three bulbs.

As a side note, if you've installed LED bulbs, they don't draw enough current to make the flasher work. You have to either replace the flasher with an electronic one, or add resistors to each signal circuit.
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Monday, September 8th, 2014 AT 7:47 PM

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