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TOPIC: Trailer led light problem

Trailer led light problem 2 weeks 1 day ago #9249

  • 1926Gnasher
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New car transporter trailer fitted with led lights - all electrics working normally attached to everyday car - 2015 Audi - but when hooked up to our Sprinter based van [2017] a problem develops[which doesn't show with an older trailer which is also led ]. Everything works normally as long as no more than one function is used but as soon as ,eg indicators + brake lights ---> error message pops up on dash and indicators flash at much higher frequency. My first thought was earthing problem but could it be that the new led's do not draw enough current and so the Merc. thinks there is a fault?
Anyone else had this problem? I have had a search for a towing adaptor with an inbuilt load resister but not found anything yet. Any suggestions ?
Jon
Last Edit: 2 weeks 1 day ago by 1926Gnasher.
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Trailer led light problem 2 weeks 16 hours ago #9250

  • Alanedwin
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I got this from a sprinter forum I'm on.

Oh, the joy of LEDs....

The problem is that LEDs are highly efficient. It only takes 10 to 20 milliamps to get them to glow.

A typical incandescent tail light bulb is 5 watts, which means they need over 400 milliamps to light up.
(a brake light or turn signal is 21 watts .. so that's 1750 millamps)

The Sprinter's transistorized light drivers simply don't bother to fully turn "off". They almost get there, but don't.
And the leakage current they're still delivering is enough to brighten the lives of an LED.
(in an incandescent bulb the diddly current wouldn't even begin to make it warm up, let alone get to visible temperature)

Putting a resistor in series won't solve it... you need LEDs that have a low-ohmage resistor directly across each "bulb", hopefully effectively short-circuiting enough of the leakage current around the LED to keep it off.

Yes, poor grounding can also cause symptoms like this (any stray currents try to go through the bulbs), but usually a poor ground sends the current "backwards" through some of the bulbs, which may or may not illuminate an LED, depending upon how it's constructed.

--dick
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Last Edit: 2 weeks 16 hours ago by Alanedwin.
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Trailer led light problem 2 weeks 1 hour ago #9251

  • 1926Gnasher
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Thanks Dick ,
I thought it would not be as simple as an inline resister - these things are never that easy to sort out. With my old trailer I converted to leds a few years ago after the usual problems of those rubbish bulb holders fitted to most. The sprinter is quite happy with that set up, and Audi with both old and new, but the sprinter doesn't like the new one .
Jon
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