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LED trailer lights -help!

Discussion in 'LEDs and Optoelectronics' started by ajstars, Sep 2, 2014.

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  1. ajstars

    ajstars

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    May 10, 2014
    I have just spent all day wiring in parallel, four led side marker lights to my trailer. Two are 12 volt lights (ebay ID 370832771146) and two are 12/24v lights (ebay ID 221365738132) but none of them work. Have I done something that can't be done?
    Help appreciated.
    Thank you
     
  2. Gryd3

    Gryd3

    4,098
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    Jun 25, 2014
    Are you certain you connected the polarity correctly? This is not a problem with incandescent bulbs, but is with LEDs.
    Where did you pull power from?
     
  3. ajstars

    ajstars

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    2
    May 10, 2014
    I did not test each LED first but wired all the blacks to the negative and all the yellows to the positive side. The feed is taken from the back of the trailer socket. When I plug in my trailer light board everything works ok. There was one problem which I rectified - which was a short between two wires and it blew the 10a fuse on my cars side light circuit. I have in fact wired up both left and right sides with the four LED parallel circuits as described and each side takes its feed from separate side light circuits (left and right). The negative is of course connected to the one pin though.
     
  4. Gryd3

    Gryd3

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    Jun 25, 2014
    My only recommendation from here is to ensure that the connections are electrically sound and that the power and ground from the trailer plug are in good condition. Depending on the circuitry inside your lights, they may not come on at all if the supplied voltage is too low which could be caused by a poor connection or bad ground.

    I take it you would like to avoid removing one of the light to test independently?
     
  5. ajstars

    ajstars

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    May 10, 2014
    It's on a boat trailer so I soldered every connection, heat shrunk then wrapped in self amalgamating tape!!
    I will double check the earth but as the trailer lights all work with normal bulbs I can't see it being an earth problem. Also there was continuity between the left hand circuit and the earth pin when I tested it after it shorted out which would suggest the earth wires are connected behind the trailer socket! It's got me stumped.
    Would I be correct t in saying the different types of LED will make no difference as they are connected in parallel?
     
  6. Gryd3

    Gryd3

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    Jun 25, 2014
    Yes and No.
    LED's require some kind of driving circuit or protection.
    Cheap setups use resistors, better setups (usually) use some kind of current control circuit.
    If these devices are used with the LEDs, then you can mismatch and mix your LED modules in parallel and be fine. They are usually included for automotive LED lighting inside the enclosure.
    If this device is provided as an 'external' required accessory like a transformer, then you must carefully follow the installation instructions. Mixing LEDs after this device is a bad idea. (This device is usually built in to those types of LED enclosures though. An example of when they are not is kitchen LED puck/strip lighting requiring a transformer)
    Additionally, if the manufacturer skipped using these things it could be very bad and they are most likely burnt out already. This is unlikely though as the seller would be long out of business.

    Those lamps appear to be sealed as well, so taking the amber housing off wont work...
    I hate to say it, but the only thing I can think of from here is clipping the wire to one of your lighting modules and testing it by itself. Perhaps the manufacturer accidentally swapped the yellow and black wires leading you to unknowingly hook them up backwards...
    Was there any documentation sent with the lights? Robust products have reverse polarity protection... I'm hoping the paperwork sent with them says something about it. Either as a big No-No, or as a troubleshooting step. 'If these don't work swap polarity'.

    Don't actually swap the wire while you test one of them though... it could be a very bad idea if the device does not have built in protection for it.
     
  7. ajstars

    ajstars

    20
    2
    May 10, 2014
    The button LED is definitely using a resistor, the amber ones I have no idea though. They came with no paperwork so I guess I will have to either get some more to try or start cutting into the loom again.
    Thanks for all the help.
     
  8. ajstars

    ajstars

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    May 10, 2014
    Ok I will be the first to admit I did something rather stupid. I had wired the socket end of the trailer lighting circuit the wrong way - putting the positive as the negative and one negative side as positive, hence why one side didn't work as it was wired with polarity reversed and the other side simply had no power! It's that middle pin, for some reason I always think it's the negative but that would just be logical!
    Big thanks for the advice though, you kept me sane enough to go and check it one more time!
     
    Gryd3 likes this.
  9. Gryd3

    Gryd3

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    Jun 25, 2014
    Not a problem. Glad you got it figured out. Did you have to cut out a light to figure that out? Or were you lucky enough to find it another way?
     
  10. ajstars

    ajstars

    20
    2
    May 10, 2014
    I cut off one light which was broken anyway and I intended to replace it, that worked across a battery so I knew the LEDs were ok. I could see resistors in the amber lights so there should have been no problem mixing the lights which pointed to the only thing I had not checked which was the plug end of the wiring loom and as soon as I opened it I saw my mistake.
     
    Gryd3 likes this.
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