07 Silverado Tail Light Wiring Schematic?

Discussion in 'Chevy Truck Forum' started by JustDanMI, Aug 30, 2009.

  1. BernieB

    BernieB Senior Member

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    Exactly the opposite Dan. LED's draw so much less current that old style flashers (signals and 4-way) wouldn't work with them.

    Typically, an LED taillight will draw about 1/10 the amperage that a regular incandescent bulb would. With old style "standard" flashers that meant that not enough current flowed through the flasher to heat the bi-metallic strip (which bent to open and close the contacts) so they never flashed, or flashed very rapidly (because the strip cooled quickly). However, if you install what is normally called a "heavy duty" flasher they will work just fine.

    Heavy duty flashers don't depend on the current going through them to the bulbs in order to flash. Instead, they have a built in resistor that provides the "load" needed. They were originally made for use on vehicles towing trailers, because the lights on the trailers added to the current draw and overheated a standard flasher. The standard one would flash once, then stay open, or just barely let the bulbs flicker. As a matter of fact, I had that exact same problem on my GMC when I first bought it. The turn signals would suddenly stop working after the truck warmed up and they got used a couple of times. Turned out the normal heavy duty flasher had been replaced with a cheap standard one, and the heat from the engine (June in Florida, with a diesel) was just enough through the firewall that the flasher got too hot. :)

    Now, they do sell special "electronic" flashers for use with LED's. The only difference between them and a heavy duty is that the electronics also have additional circuits in them because some vehicles have odd flasher circuits, and adding LED's to them can lead to problems, like brake lights not working. I believe this is a problem only on vehicles with those oddball turn signals where there are separate lamps on the front and the sides that alternate when they flash. Not 100% sure on that though.
     
  2. crabtruck

    crabtruck Senior Member

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    Bernie give me a break,
    I'm to busy typing what was already said
    to read what it was ! :eek:

    Dan I don't think this place ever runs out of opinions
    though a lot of times we forget the question :D

    LED concept was to be brighter at reduced electrical loads.
    Now that the entered the toy catagory instead of just straight replacements,
    the load of an LED setup could exceed the factory supply.
    To be sure you should do the math yourself
    (sometimes that's just reading the package).

    One misconception some folks get fed to them is that
    by replacing with a LED fixture the power draw (wattage)
    will be less. Not if the manufacturer is trying to avoid complaints
    about the flashers going to fast or car telling you bulb is burnt out.
    So what they do is basically add a resistor across the LEDs to draw
    more current so the flasher thinks all is good. It is all good, but
    you have not cut the load one bit. Read them or measure them.

    Trailer lights are on seperate fuses for many new trucks
    and the fuses are somewhat more forgiving because they are not
    supplying the trailer with truck so it's an "unknown".
    Figure your total loads and don't get to close to fuse rating.

    Dang it, Bernie, you're still typing too fast for me, I see you got to
    some of this already. I don't care, I'm still posting it. :p :D
    :rofl:
     
  3. JustDanMI

    JustDanMI Full Member

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    ok guys, ran into a little snag I should have picked up earlier. I got my light tester and started checking all of my wires going into my trailer connection. I was able to find every wire I needed but one. the brakes.

    When the brakes are applied, the right and left turn wire both trigger the light with a solid signal. No other wire lights up, except for the brown parking lights wire. The instructions with the light bar mentioned the possibility of having to connect to the 3rd Brake light.

    Now, Do you happen to have an idea of something I may be missing? Or do I really need to try and figure out where in the world I can connect to to the 3rd Brake Light?

    I was thinking the blue electric brake wire would give me my brake lights as well. But upon closer inspection of the wire diagram that bernie sent over, I noticed that it stated a converter was required to use a brake wire.
     
  4. BernieB

    BernieB Senior Member

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    JC Whitney sells the converter you need. It's really inexpensive, around $10 I think. It's used for adding a third brake light to a vehicle that doesn't have one. It has two inputs, one output and a ground. The two inputs go one to each brake light, and the output goes to the third brake light, or in this case, the brake input for your light. Basically it acts as a pair of logic gates. If no input, or if either input goes high (gets voltage) the output is low (no voltage), but if both inputs go high at the same time then the output goes high also.

    http://www.jcwhitney.com/LOGIC-CIRCUIT/GP_2003583_N_111+10201+600003037_10101.jcw

    But, the simpler way is to just hook up to the blue wire, as that will go hot when the brakes are applied. No need for any converter. :)
     
  5. BernieB

    BernieB Senior Member

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    Um... you do have an electric brake controller in the truck, right?
     
  6. JustDanMI

    JustDanMI Full Member

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    To be honest, I have no idea if there's an electric brake controller. I do know I have no juice to that blue wire when the brakes are pressed. I was assuming that meant I didn't have a brake controller. And if the blue wire doesn't trigger the test light, I was assuming it wouldn't work for my brakes either.
     
  7. BernieB

    BernieB Senior Member

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    Yup, no juice means no electric brake controller, which also means you're limited to a 1,500 lb trailer (or less) depending on your state laws.

    You'll need the logic circuit from JC Whitney then. The good news is that it's under $7 (they have two), the bad news is they kill you on shipping for it. It's an epoxy sealed unit, so it can stay under the truck with no worries.
     
  8. JustDanMI

    JustDanMI Full Member

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    I noticed a review on the jcwhitney site saying that the blinkers bled over into the brake function still. I might see if I can find one on another site with better reviews.

    That light bar actually came with a couple resistors and a capacitor. Not sure where I would use those if I needed them.

    I'm even willing to route a wire to the CHMSL wire..........if I knew where it was. I looked under the dash, and nothing clearly called it out. Guess it's time for more research.
     
    Last edited: Sep 6, 2009
  9. BernieB

    BernieB Senior Member

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    Well, when we added the cap to my g/f's Dakota a few years ago I bought that exact part from JC Whitney, installed it and it worked perfect. No problems at all with it.
     
  10. JustDanMI

    JustDanMI Full Member

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    Thanks Bernie, I'll try ordering one and see how they work for me as well than.
     

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