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  1. #1
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    Default Why do LED festoon bulbs still glow when switched off?

    I bought 4 festoon LED replacement globes from reputable dealer assuring they were Canbus compliant . Passenger dome light works fine , drivers dome light has a dull glow when switched off ( maybe has something to do with it being one of the lights that go dimm and then off when the door is closed ) The two number plate lights come on for two seconds then go off then on and off . Can I leave the drivers dome one in even if it has a slight glow and why would the number plate ones ocilate all the time. I am sure I will have no issues returning them.

  2. #2
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    Default Re: Why do LED festoon bulbs still glow when switched off?


  3. #3
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    Default Re: Why do LED festoon bulbs still glow when switched off?

    On old school cars you see something similar, and also only on the festoon type. On my old Nissan, mine glo brighter and brighter as the humidity goes up. In the rain mine nearly seem to be around 20% normal brightness. Some say it's just because they work on such a small amount of power, that the induction from other cables cause them to glo.

    I have checked with two other Hardbody bakkies of the same vintage, and both have the exact same problem with these globes as cab lights. So I live with it. It does not run my battery flat, although, I have already left my door open for over a week, and they were not able to dent my 120Ah battery, so no worries.
    David/Hillbilly - 1997 SFA Nissan Sani 2,7 TD - 5" lift on 33" tires - Dual Transfer with 4.1 gears

    http://www.youtube.com/user/davidabcab



  4. #4
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    Default Re: Why do LED festoon bulbs still glow when switched off?

    Imho it's a leakage current or reverse current flowing in the negative wires that triggers the Led to glow. You can insert a resistor in series and it will stop the glow. The old globes had a resistive filament so this prevented the globe from glowing. I'm under correction.
    Isuzu STD 2.5d 2x4 rear diffy lock
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  5. #5
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    Default Re: Why do LED festoon bulbs still glow when switched off?

    Due to the electronic controllers, positive is supplied continuously with the negative being disconnected when off, then alternatively negative is supplied when on. (Negative switching) The residual resistance in the wiring etc is sufficient to let the globes glow.

    Can bus globes normally just have an extra resistor to let the controller know that is there and is functioning correctly, but will still allow the globe to glow. Resistors can be added to kill the glow but need to be rated for higher amperage as they will get hot, you will need to measure the amperage first to determine the resistor size. Interior lights are small amperage but trailer lights etc are high current.
    Everything should be made as simple as possible, but no simpler.

  6. #6
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    Default Re: Why do LED festoon bulbs still glow when switched off?

    It's not just automotive lamps that do this, I have a few LED house lights that do that.
    One is an E14 candelabra type, other is an E27 bedside lamp. The E14 has a slight glow for a much longer time than the E27 does.
    Cheers,
    John Kilfoil

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  8. #7
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    Default Re: Why do LED festoon bulbs still glow when switched off?

    Thanks for replies, I will probably just leave the dome light one in and replace the numberplate ones . I know for the 220v LED globes and flood lights to prevent the glow I just swop the line and neutral around and this solves the problem.

  9. #8
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    Default Re: Why do LED festoon bulbs still glow when switched off?

    Quote Originally Posted by JohnnoK View Post
    It's not just automotive lamps that do this, I have a few LED house lights that do that.
    One is an E14 candelabra type, other is an E27 bedside lamp. The E14 has a slight glow for a much longer time than the E27 does.
    Mine too, I've even disconnected the live in the switch and it continued to do so, electrician said not too worry, I thought I'd discovered free power

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  11. #9
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    Default Re: Why do LED festoon bulbs still glow when switched off?

    Quote Originally Posted by IcePick88 View Post
    This guy is hilarious. Gotta love his description of himself, which is now in my signature.
    Cheers

    ZS5KAD - PROFFESIONAL DUMBASS
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  13. #10
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    Default Re: Why do LED festoon bulbs still glow when switched off?

    Quote Originally Posted by Fluffy View Post
    This guy is hilarious. Gotta love his description of himself, which is now in my signature.
    Absolutely brilliant, makes me think of our newly qualified electricians
    Isuzu STD 2.5d 2x4 rear diffy lock
    2x spotlight,2x fog lights
    215/80/R15c tyres
    1 x great humourous driver
    GPS,Bluetooth
    Eagle eye dash cam --stolen ..bought another one
    snorkel soon
    Craig
    I DON'T LIVE IN AFRICA,AFRICA LIVES IN ME- Kyle my son

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