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Ram 1500 brake light

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Dutch View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dutch Quote  Post ReplyReply Direct Link To This Post Topic: Ram 1500 brake light
    Posted: 14 Aug. 2015 at 4:08am
Hi all,
Kind of an odd thing occurring on my ram truck.
I added a cap and wanted to wire up the third brake light. Internet search shows a single wire protruding out of the harness near the spare tire as the power source for the additional light. I tested it sure enough it gives me the Required voltage when the pedal is depressed. Hooked it up an good to go.
Now comes the odd part. Took the dogs out after dark and noticed that the 3rd light on the new cap was glowing ever so slightly indicating there was power when there should not have been. Unwired and tested the "proper wire" and the is a steady 3volts all the time, obviously enough to power the LED light but why is it doing this?
I suspect it has something to do with the Ebrake controller but anyone that knows me knows wires and I don't get along.
If anyone can guide me I'd sure appreciate it.


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MarkB View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MarkB Quote  Post ReplyReply Direct Link To This Post Posted: 14 Aug. 2015 at 4:28am
The led needs very, very little power to glow. Since most electrical systems have a very small of current bleeding throughout the wires you are getting the glow. A normal bulb wouldn't be effected by the tiny current but LEDs are super sensitive. Even if it was .5 volt you'd probably get a glow.

You could search for a resistor to put into the wiring that might kill the glow.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dutch Quote  Post ReplyReply Direct Link To This Post Posted: 14 Aug. 2015 at 11:45am
Thank you for the response and suggestion. I thought about this but figured I would only be masking the real issue.
I will have one of my electrical guys recommend an in line resistor and give it a try.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 67charger Quote  Post ReplyReply Direct Link To This Post Posted: 14 Aug. 2015 at 11:46am
3 volts seems to be a lot of voltage for a wire that should be only activated by a switch.  Do your normal brake light wires have three volts on them too when the brake pedal is not pressed?  I would think that the battery would be drained pretty quick with three volts being drawn?  I have been more wrong than right though?  I would check your wire going to the trucks brake lights and see if they have 3 volts too.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dutch Quote  Post ReplyReply Direct Link To This Post Posted: 14 Aug. 2015 at 5:41pm
Charger, I thought of that and checked, there is no power at the brake light until the pedal is depressed, this is why I thought possibly the Ebrake controller.
3 volts is a lot in my book too, but just now I went out and found the same colored wire coming from under the dash ( near the controller) to the fire wall. It measures exactly the same as the wire at the rear of the truck that I am supposed to tap into. I do not think it is a coincidence and believe the Ebrake is the source of the 3 volts.

Now the question is, should it be doing this? Another question is will this drain my battery if left as is ( I think yes).

If it should be doing this then someone, somewhere makes a diode or resister to stop it - else my factory controller is whacked...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 67charger Quote  Post ReplyReply Direct Link To This Post Posted: 14 Aug. 2015 at 6:44pm
Could you just wire the third brake light into the brake light lines going to the rear on the truck "splice"?  Or better yet you could just wire it into your trailer brake lights wire going into the trailer connector.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dutch Quote  Post ReplyReply Direct Link To This Post Posted: 14 Aug. 2015 at 9:59pm
I can't tie into the truck brake lights because of the turn signals are intertwined and it junks up the flashers. ( been there)
I will investigate the trailer brake line - that might be the best alternative.
Another idea I had was to run the Ebrake wire from the ignition switch BUT, I am concerned about future issues.
Anyway I do appreciate the council...
I will let you know if it works out.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dutch Quote  Post ReplyReply Direct Link To This Post Posted: 20 Aug. 2015 at 2:36am
Ok so the trailer plug wiring is also tied into the turn signals so that option is also out.
I did a little more reading and ram charges the harness with a small voltage to search for burned out bulbs... Incandescent bulbs are unaffected however there is enough power to light the LED light.
Solution was to install a 100 ohm resistor in the circuit to filter out the stray voltage.

Thanks for the input and I hope this helps someone else down the road.
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