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Led's headlight issue

Discussion in 'LEDs and Optoelectronics' started by portishead, Aug 3, 2016.

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  1. portishead

    portishead

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    Apr 5, 2016
    Hi all,
    I dont know if this is the right place... But I am after a little help. I have swapped out my daytime running halogen bulbs in my car for a couple of led bulbs. These bulbs (only £10) Nothing expensive say they are canbus error free however, the bulbs work nicely but bring up the warning lights on the car error system. I guess the leds are less power and the car thinks the bulbs have blown?? Does anyone know a work around for them or what I could use to correct it???

    These are the bulbs if its of any help....

    Thanks all

    http://www.ebay.co.uk/itm/252415530198?_trksid=p2057872.m2749.l2649&ssPageName=STRK:MEBIDX:IT
     
    Last edited: Aug 3, 2016
  2. Alec_t

    Alec_t

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    784
    Jul 7, 2015
    Presumably the LED bulbs have inbuilt (or associated) electronics for current control? If so this will interfere with the bulb tests the car does.
    BTW, have you checked with your insurer that they're happy with the modification to your car? Some insurers can be picky and may invalidate the policy.
     
  3. Tha fios agaibh

    Tha fios agaibh

    2,112
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    Aug 11, 2014
    I would put the original headlamps back in, measure the current they draw and see if the fault goes away. Then, reinstall your leds and check amperage again. The error free leds should have a resistor added so they draw the same current.
    I assume these are made to fit your car model?
     
  4. portishead

    portishead

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    Apr 5, 2016
    Yes they are made for the car , well for the particular terminal type anyway. Seller states the f30 BMW anyway. Standard bulb design holder.
    I have swapped the originals in and out several times the warning fault goes instantly . The originals are24w bulbs.
    How would I check the amperage on my multi Meter? ?
     
  5. Tha fios agaibh

    Tha fios agaibh

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    Aug 11, 2014
    Screenshot_2016-08-03-16-10-47-1.png Use a clamp on DC meter or an ammeter capable of handling at least 2amps.
    You can break apart the wiring at a splice point in the light circuit or pull the fuse and insert the leads across it to complete circuit.
     
  6. portishead

    portishead

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    Apr 5, 2016
    Thanks. I'll try it on daylight and let you know results
     
  7. Bluejets

    Bluejets

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    Oct 5, 2014
    24w for headlight bulb seems rather small.
    55W would be normal.
    55w/60w for low/high beam.
     
  8. portishead

    portishead

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    Apr 5, 2016

    So, testing as you mentioned. I have my meter set on dca 20. The led shows 0.12 & the halogen is 1.71. Both sides are the same. Is this the difference that causes the problem? If so can we fix or adapt ?
     
  9. Sunnysky

    Sunnysky

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    Jul 15, 2016
    Instrument panel will have some threshold current sense to detect faulty halogen filament.
    Thus a dummy load current perhaps 1 A is needed or 14W. This is Trial and error to determine lamp fault threshold indicator on instrument panel.
     
    sundy likes this.
  10. portishead

    portishead

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    Apr 5, 2016
    So, when it gets to component level I need pointers!!! What should I be looking to buy? And from where?
     
    Last edited: Aug 6, 2016
  11. portishead

    portishead

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    Apr 5, 2016
    So what your saying is I need to add in another light bulb behind the led to make the led work and not bring on the warning light? Cant be a permanent fix surely! !
     
  12. Sunnysky

    Sunnysky

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    Jul 15, 2016
    Other than finding the threshold for bulb resistance in the instrument panel self test, I think so, or just ignore it. The LEDs work but the lamp fault light is ON.
    This is a common issue.
     
  13. portishead

    portishead

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    Apr 5, 2016
    I thought i had to solder a resistor . Would it get hot?
     
  14. Sunnysky

    Sunnysky

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    Jul 15, 2016
    yes.
    A bulb has resistance and gets hot, but wears out.
    A resistor gets hot also and must be larger to run at a lower temp.
    Trial and error testing would determine the best value, starting around 10 Ohm 5W rating but uses 1.4W.

    I Have no idea what current is needed to turn off fault lamp .

    If you had 2 same halogens in series, current would be = 1.71A /2 = 0.85A and 14.2V/0.85A= 16.7Ω

    Then you could use 16Ohms or so ... This is trial and error. The least hot part that works is best..
     
    Last edited: Aug 7, 2016
  15. Tha fios agaibh

    Tha fios agaibh

    2,112
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    Aug 11, 2014
    10 ohms sounds good, but how did you get 1.4 watts?
    I was thinking that .12a would be drawn by each led with supplemental parallel resistors added of about 9 ohms that would draw an additional 1.47a totaling near the original 1.71a drawn by the bulbs. This would require 25watt resistors.
    (Assuming 13.2 volts)
     
  16. Sunnysky

    Sunnysky

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    Jul 15, 2016
    I used 10 Ohm or 1.4A roughly 82% power point. You can start anywhere like two halogens in series as half power to hunt for the threshold.
     
  17. Tha fios agaibh

    Tha fios agaibh

    2,112
    713
    Aug 11, 2014
    Sunnysky, your 5 watt recommendation sounds way too small. (Or am I missing something?)
     
  18. Sunnysky

    Sunnysky

    480
    121
    Jul 15, 2016
    sorry. 20W
     
    Tha fios agaibh likes this.
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