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led lighting problem

Discussion in 'Tips and Tricks' started by fupabox, Apr 16, 2010.

  1. fupabox

    fupabox Active Member

    I'm in the process of swapping as many of my lights for leds as I possibly can..I have done the whole dash,3rd brake light and the rear signals (hijet) have some more leds coming but I have an odd problem..I replaced the rear combination brake tail-lights with red 24 led dual function bulbs..worked perfectly for 2 days then my brake lights wouldn't turn off??...after checking everything including the brake switch,I have traced it down to the right rear....if I put a regular dual filiment bulb in that socket the brake lights work fine..with any led dual bulb the brake lights will not go off...conclusion is that there is enough juice from the taillight wiring leaking into the brake circuit to illuminate all my brake lights,but with a regular bulb in the socket,there is sufficient resistance to negate the effect...checked all the wiring and can not find any dodgy connections or crossed wiring......any thoughts ?? I picked a bad week to lend my electrical tester to a dude 70 miles away:frustration:
     
  2. fupabox

    fupabox Active Member

    The turn signals have been fine actually other than they flash quicker..haven'y done the fronts yet though and with them in the circuit resistance my then become a problem as you say.....my buddy next door converted his Volvo 18 wheeler over to led a few months back and says the reduced draw on the alternator is a huge bonus...he showed me some stats on the extra benifits of led for brake lights and the quicker lighting of the leds when you hit the brakes actually gives the person following you an extra 30-40 ft of reaction time
     
  3. cabnfever

    cabnfever Member

    interesting, i was thinking about this myself for my truck as i have done a few led's in my house.

    fupa, i remember we tried doing this on a mid 80's/early 90's vw jetta and the same result happened on the 3rd brake light. As im into early vw rabbits from what i understand there are resistance issues and cant be done on them. You are probably having the same issue.

    Now i have to go all around my sambar and see what bulbs i have to change over lol
     
  4. fupabox

    fupabox Active Member

    I'm sure it is a crossed wire somewhere as it didn't misbehave for the first few days
     
  5. Stuff99

    Stuff99 Active Member Staff Member

    I know on older cars when you do the LED conversion you need a LED signal light flasher. basically you lower the resistance too much.

    as for the brake light, Ive never heard of that not working right.
     
  6. fupabox

    fupabox Active Member

    finally got around to checking it...seems there are .45 volts coming through the brake light circuit (on the drivers side only )when brakes aren't on....doesn't bother the regular bulbs but is enough to permanently light all the brake lights when a LED is put in..
     
  7. o8k

    o8k Member

    Sounds like somthing a Diode may cure?

    However, it is weird that the LEDs themselves forward bias with 0.45v being that they are just diodes that consquently make light.
     
  8. fupabox

    fupabox Active Member

    I thought that was odd as well...a diode should only allow current to flow in 1 direction which is why they always have a pos and a neg side? or am I wrong on that?
     
  9. Stuff99

    Stuff99 Active Member Staff Member

    ya i think diodes are one way electrical valves.
     
  10. o8k

    o8k Member

    Diodes also drop voltage when fwd biased. Typically 0.7v is the drop and the potential diff needed to open. so the diode may just block the 0.45v your seeing in the "off" state. When you turn on your lights, the diode will then fwd bias and consume its 0.7v pay for its job. y will need to know the amp draw to determine what power diode u need. 0.7v times current equals how much power in the form of heat it will consume for its job. I bet diodes can be found in lower voltage flavors these days too.

    EDIT: Im making the asumption that someone else (original or aftermarket circuit designers) put a current limiting resistor in there some place. and all you need to do is block a little voltage. Perhaps a bad asumption. Best thing to do is look at post #15 b4 doing anything.
     
    Last edited: May 17, 2010
  11. o8k

    o8k Member

  12. o8k

    o8k Member

    Last edited: May 17, 2010
  13. o8k

    o8k Member

  14. o8k

    o8k Member

    please forgive my constant hammering on this thread... But this is also helpful info...

    Summary: Changing to LED bulbs drops the current useage and freaks out your flasher module in one of two ways: "1. Most commonly it will flash too fast, about 2.5 cycles/second instead of the 1 cycle/sec that you're used to. This can be annoying for some people. 2. The lights might not blink at all, but just stay on constantly. " --from site below SOLUTION: get a different flasher module or load the system with more current. (i kinda like my idea of the diode though, hehehe, but it probably wont work if the flasher is going wonky).

    http://www.bugmanweb.com/gsxr/flasher.html
     
    Last edited: May 17, 2010
  15. Acerguy

    Acerguy Moderator Staff Member

    I think it's cool stuff! Thanks for posting it.
     
  16. fupabox

    fupabox Active Member

    I agree.it is helpful... thanks for the info o8k...... my led turn signal swap was no problem ..I had already assumed they would flash more rapidly and they do slightly, but it isn't anything I can't live with.I still need to isolate that voltage leak in the drivers side taillight...it seems to be the cause of the brake lights coming on. After reading the gizmodo article I think I'm wanting UV leds in the dash to make everything glow:) I'm like a chimp when it comes to shiney stuff....ooook:)
     
  17. greg0187

    greg0187 Moderator Staff Member

    The LED is a diode (Light Emiting Diode). I don't think adding a diode will help you much. I think your best bet is to find the culprit or use a resistor. The resistor decieves the purpose of reduced amp draw though. I'd start with the brake light switch at the pedal...
     
    Trey 4x4 likes this.
  18. erixun

    erixun Bronze Supporting Member

    Maybe you have "Zener Diodes" some how, which allow current in both directions at preset levels. Don't know why you would, I only saw those installed on a couple of things in the military....
     
  19. fupabox

    fupabox Active Member

    Nope not zenners...I have those in my Saeco automatica coffee machine..they kind of flicker like a candle:)
     
  20. fupabox

    fupabox Active Member

    Well I had some time to tackle this again ....the simplest explanation as usual is the answer..the dual contacts on the base of the bulb...one is slightly miss aligned and making just enough contact with the brake circuit to send power to the brake light when the taillights were on:eek:...slight surgery on the bulb base contacts and the problem is solved ....I'm 80% led now..even changed the halogen H3 foglights to h3 smd leds ($6.95 inlcuding shipping for the pair) I've got replacements for the license plate bulb and interior lights on the way..headlights will be the only non LED on the truck ...once they are all in I'll post the amperage draw..then swap them all back and check the difference....My hope is to increase voltage to the coil at all rpms(reduce slight voltage irregularity would be a better way to put it) with the reduced power requirements of the LEDS..I already seem to have a smoother idle..
     

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