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Discussion Starter #1
I removed a LED center light from car in a junk yard a while back. I tested the light by touching the two wire leads to a battery. The light works. I mounted the light in the center of my package tray and it mounts flush against my rear window. I ran the two leads (red and black) between the package tray and the rear window into the trunk. I attached via a scotch lock the red wire to the brake light lead where the wires are routed through the car on the inside the left side of the trunk, and grounded the black lead to the body via the bolt on one of the rear speaker mounts. The center LED brake light works when I hit the brakes. The problem is the center LED light also flashes when I turn the right turn signal on. I tried attaching the red wire to different leads of the truck harness but either the center LED light flashes when a turn signal is on either left of right depending upon which lead it's connected to, stays on when connected to the tail light lead, doesn't work at all, (I assume I'm connected the red wire to a ground, or works as I originally described, brake light on and flashed with right turn signal on.

Any suggestions would be appreciated.
 

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Discussion Starter #4
I did the same, but had to run a new wire from the brake switch (at pedal) which stopped the turn signal problem. It does light up when the head lights are on, but still works fine as a third brake light.
Thanks I'll try that. My brake light switch on under the hood as I have a 64 1/2. Should I run wire to the wire I previously grounded?
 

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Thanks I'll try that. My brake light switch on under the hood as I have a 64 1/2. Should I run wire to the wire I previously grounded?
You can place the ground wire wherever you like. My ground wire is on the parcel shelf. You only need to run the power wire to the brake switch.
 

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Discussion Starter #6
You can place the ground wire wherever you like. My ground wire is on the parcel shelf. You only need to run the power wire to the brake switch.
Great, my ground wire is already on the parcel shelf grounded to where the speaker is mounted to the shelf. Running a wire from the brake light switch is a simple task.
 

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The problem is the center LED light also flashes when I turn the right turn signal on.
There is a "black box" you have to connect to the 3rd brake light to stop the blinking when the turn signal is on.
 

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Discussion Starter #10
There is a "black box" you have to connect to the 3rd brake light to stop the blinking when the turn signal is on.
Is that "black box" something I should have removed from the donor car in the junkyard when I got the center light?
 

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If you're good with electronics I think what you need (and what's probably in any black box) is an AND logic gate to turn on the CHMSL only when both the left AND right brake light are on. So two relays or transistors in series that both have to be turned on in order for power to go to the light.

Or run the separate wire to the brakes switch. I think that's what most modern cars do anyway.
 

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Leave it! I don't think the 3rd brake light flashing is all together bad. Anything up to throwing things at the people behind us is not a horrible idea! Now if that light had two elements that could be divided L/R would be even better:)
 

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Leave it! I don't think the 3rd brake light flashing is all together bad. Anything up to throwing things at the people behind us is not a horrible idea! Now if that light had two elements that could be divided L/R would be even better:)
 

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Easiest for you would be to insert a diode between each brake light and your third brake light. A 1 amp diode should be plenty. Basically a diode is a 1 way valve for electricity.
 

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You need a third brake light logic module. Something like this; LED or Incandescent bulb Brake light Logic module. These have been around since the 80s. There are also many new modules that I am unfamiliar with. This one looks simple enough; Pacer Performance 20-702 Black Logic Circuit. Some work only with LEDs and some have functions like strobe lights. No thanks to strobing brake lights. If you want to see strobing brake lights just get behind a slow-moving Subaru with a scared driver. Don't wire it so it flashes with one of the signals. That just screams "I didn't know how to wire it" to those who know. Technically, that doesn't follow lighting regulations in many jurisdictions. At least outside of Moscow.
 

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Easiest for you would be to insert a diode between each brake light and your third brake light. A 1 amp diode should be plenty. Basically a diode is a 1 way valve for electricity.
These diodes will work, part number 1N5822. You can get 30 with prime shipping for under 6 dollars. Install with lines toward third brake light.
LR------diode---3rdBrk---diode------RR
 

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By the way, with the 2 diode setup, the third brake light will flash with the turn signals or hazards until the brakes are applied, then it will be on.
 

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Diodes don't work right. You need some help from a real transistor. I think this LED logic circuit is just a big transistor;
 
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