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Discussion Starter · #1 ·
I recently purchased a nice '05 Wrangler Unlimited.
I had a couple bulbs go out in the rear, so I decided to go with LEDs.
I put in a new flasher module to deal with the hyperflashing. All's good.
Then I noticed as my wife heads out in the evening that there is an issue with the taillights.
Long story short, the taillights don't light up unless you open the tailgate.
If I tape over the door contacts for the tailgate, then I have running lights in the rear (front has never been an issue. )
However, I've discovered that that is how the 3rd brake light is powered.

To complicate things, light for the license plate is dim, so I thought that I might add a white LED above the plate (inside the housing of the brake light) so I tapped into the wiring for the brake light and added an extra white LED pointing down at the plate. With the taillights on, there is only 4.75 volts. The LED needs 12 to light up. It doesn't go to 12 unless you hit the brakes. So you get plenty of light to the plate if you hit the brakes. But only if you don't have the taillights on.

What is going on??
 

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I recently purchased a nice '05 Wrangler Unlimited.
I had a couple bulbs go out in the rear, so I decided to go with LEDs.
I put in a new flasher module to deal with the hyperflashing. All's good.
Then I noticed as my wife heads out in the evening that there is an issue with the taillights.
Long story short, the taillights don't light up unless you open the tailgate.
If I tape over the door contacts for the tailgate, then I have running lights in the rear (front has never been an issue. )
However, I've discovered that that is how the 3rd brake light is powered.

To complicate things, light for the license plate is dim, so I thought that I might add a white LED above the plate (inside the housing of the brake light) so I tapped into the wiring for the brake light and added an extra white LED pointing down at the plate. With the taillights on, there is only 4.75 volts. The LED needs 12 to light up. It doesn't go to 12 unless you hit the brakes. So you get plenty of light to the plate if you hit the brakes. But only if you don't have the taillights on.

What is going on??
That is why you only have a plate light when the brakes are on. You need to pull license plate wiring from the tail light circuit, not the brake light circuit. Also check the bolt threads that hold the light fixtures on and make sure they are clean and tight. The whole rear lighting system grounds through those bolts.
 

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Discussion Starter · #7 ·
There is no plate light circuit. The bottom of the brake light housing is clear for the light to shine through from the taillight, but no wiring at all for the plate. Even checked from the harness underneath that feeds the brake light housing. 2 wires for the brake light and one for the reverse light, which is grounded through the housing itself.
I did see a problem with the grounding on the left side, which I fixed. Maybe I should check the right side too. Thanks!
 

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Discussion Starter · #8 ·
No luck. Right side is well grounded.
BTW, there isn't even a place to mount a plate light in the housing.
 

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There is no plate light circuit. The bottom of the brake light housing is clear for the light to shine through from the taillight, but no wiring at all for the plate. Even checked from the harness underneath that feeds the brake light housing. 2 wires for the brake light and one for the reverse light, which is grounded through the housing itself.
I did see a problem with the grounding on the left side, which I fixed. Maybe I should check the right side too. Thanks!
Of the two wires that you say go to the brake light, one is the tail light wire (white/yellow) the second is the brake/turn signal wire. There are two wires because the lamp has two filiments. The ground for both is through the base and body bolts. Wire your license plate light to the white/yellow wire.
 

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Discussion Starter · #10 ·
Yes!! Not only do I now have a working plate light, ti fixed the other odd behavior!!
Thanks!
 

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Discussion Starter · #11 ·
Well it's broken again.
Running lights in the back don't turn on unless the back hatch is open.
I've checked the grounding and wires and even replaced the fuse just in case.
 

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Discussion Starter · #13 ·
In an act of desperation, I replaced the bulb in the 3rd brake light and now it's working again.
 

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The high center brake light comes directly from the brake light switch and has nothing to do with your tail lights. Only two things I can think of where the tail gate open would effect running lights would be that something has been miswired, or that there is a backfeed situation through the multifunction switch and a power draw in the high center brake light circuit in the lamp holder or wiring to it that is robbing power from the tail lights.....

Try pulling the lamp out of the high center brake light, then close the tail gate, and see if the rest of your lights work normally.
 
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