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Turn signal plug miswired from factory???

Discussion in 'Appearance' started by JPutnam, Jul 15, 2017 at 10:14 AM.

  1. JPutnam

    JPutnam Well-Known Member

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    So I installed LED taillights a while ago and that was when I learned about SRCK bulbs. Stupid things, so I ended up buying some different ones on ebay that actually turned out better and brighter. I tried the original regular wired led bulbs in the front turn signals and they would not work right. If in one way, the turn signal worked but not the parking lights, if installed reverse, the opposite. WTH!

    I removed the plug from the socket and used a multimeter to check the socket and it was a normal 3157 socket with the ground on either side. When I checked the pinout of the plug I noticed that the lt blue and black wires were flipped in the plug. It was the same for the drivers side. The harness was untouched and must have been done at the factory. I swapped the wires so that the lt blue wire was in pin 1 and the black ground wire was on pin 3. Now everything works.

    Is this how all the Trailblazers are wired? I wouldn't think so because I haven't heard of anyone talking about this.
     
  2. pell

    pell Member

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    Did the old bulbs work correctly?
     
    Redbeard likes this.
  3. JPutnam

    JPutnam Well-Known Member

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    Yeah, but they were incandescent. Still wierd though. I wonder if that is why my LED flasher was acting up.
     
  4. pell

    pell Member

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    I put LEDS on my service truck. The parts guy said to get an electronic flasher for the new lights because they use so little electricity that the mechanical (OEM) flasher does not work correctly. It was a few bucks more but it worked. Good luck.
     
  5. JPutnam

    JPutnam Well-Known Member

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    He was right. The electronic flasher worked, but I was getting current to the parking light circuit whenever the brakes were activated. I think this is the reason why. I will have to figure out where I put the flasher and reinstall it to see if it works now. I hope it does so that I can get rid of the 4 fire hazards I had to install.
     
  6. freddyboy61

    freddyboy61 Well-Known Member

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    The "miswire" worked with incandescent bulbs because they are non=polarized, whereas LEDs are subject to polarity.
     
  7. JPutnam

    JPutnam Well-Known Member

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    I get that, but what I don't get is that with the wiring setup like that there is only one ground in the socket.

    In the socket there is one pin for the ground, but that goes to a shared contractor that connects to both sides of the bulb. That is supposed to be the ground, but in the original wiring the pin is being feed by the turn circuit and the ground is on the contractor the turn should be. I don't quite understand how the bulb was grounding for the park circuit unless it was backfeeding through the park coil. Even though an incandescent bulb has no polarity, it should still not light up right in the configuration.
     
  8. Sparky

    Sparky Moderator

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    Probably was backfeeding something.
     
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  9. JPutnam

    JPutnam Well-Known Member

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    I don't know what's up with it. My neighbor gave me a set of switchbacks he didn't want and I threw them in for kicks to see what they looked like. The park and turn terminals were swapped on the bulb so I swapped the wires on one of the bulbs. They worked, but I didn't like the look of the white. It was a cool white and didn't match the Cree headlight chips. I ended up pulling the bulb out and when I did one of the wires came loose that I taped together before (didn't solder yet.)

    I messed up and wired them back in the factory configuration and when I tested it out the white light was only working, but in the same configuration as the corner light. I swapped the leads again on the bulb to get the amber led's to light and the effect was amazing. It is like an amber-only switchback if you know what I mean. This way the bulb flashes on and off instead of changing brightness which is usually not noticeable with bright headlights.

    Anyway, to sum up my rant, with the stock wiring and a swap of the flashback leads you can get amber-only flashbacks. You could just tap into the corner light circuit like I was going to, but this one seems safer: less load on the circuit.
     

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