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  1. #1
    Join Date
    Mar 2010
    Location
    Highlands (North of Inverness)
    Posts
    1,248

    OK Numpty question time

    I have decided to go with LED’s for my warning lights on my dash and have been told that I need to put a power resistor on the ignition/battery warning light and on the oil pressure one. Would it be fair to say that I should be putting one on all of the warning lights and if so what ones do you recommend?

    Thanks.

    Paul.
    Best anti speeding device - a rear view mirror with a police car in it.
    A pedestrian - someone who thought there was still a couple of gallons in the tank.
    AK Chassis and body collected 12.12.14

  2. #2
    Join Date
    Aug 2004
    Location
    Christchurch, NZ
    Age
    61
    Posts
    2,551
    If you are buying 12V LEDs for automotive use they will already contain the series resistor and you can use them as is.

    If you are using 'bare' LEDs (electronic component) you will need to have a 0.25A 1 kΩ in series with each. If your chosen LEDs seem a bit dim with this, lower the resistor value slightly, say 800Ω.

    Remember that unlike bulbs, LEDs have polarity - they won't work at all if you connect them the wrong way round.

    The charging light might need extra attention, it depends whether the 20mA through the LED is enough to start the alternator.
    Last edited by mylesdw; 09-04-19 at 07:28 PM.
    Cheers

    Myles D-W

  3. #3
    Join Date
    Mar 2010
    Location
    Highlands (North of Inverness)
    Posts
    1,248
    Hi Myles,

    Thanks for the reply. I am using the chrome bezel ones from car builder solutions here in the UK. I’ll send them an email to make sure the have the resistor fitted.

    Many thanks.

    Paul.
    Best anti speeding device - a rear view mirror with a police car in it.
    A pedestrian - someone who thought there was still a couple of gallons in the tank.
    AK Chassis and body collected 12.12.14

  4. #4
    Join Date
    Aug 2004
    Location
    Christchurch, NZ
    Age
    61
    Posts
    2,551
    They will have the resistor if they are rated 12V.

    The simplest way to get the charging light to work would be to keep the original lamp in circuit; tuck it up behind the dash, and put your new LED across it (across the two teminals, again, must be right way round)
    Cheers

    Myles D-W

  5. #5
    Join Date
    May 2016
    Location
    Barnsley
    Posts
    80
    Hi Paul,

    PM me, you do need a resistor to make these work as I used exactly the same items. I’ll send you full wiring diagram on email.

    Regards

  6. #6
    Join Date
    May 2016
    Location
    Barnsley
    Posts
    80
    Clear your inbox Paul, cannot reply to PM. Send me your email and I’ll drop you wiring diagram.

    Cheers, Bence

  7. #7
    Join Date
    Mar 2010
    Location
    Highlands (North of Inverness)
    Posts
    1,248
    Cleared and pm sent with my email address.
    Best anti speeding device - a rear view mirror with a police car in it.
    A pedestrian - someone who thought there was still a couple of gallons in the tank.
    AK Chassis and body collected 12.12.14

  8. #8
    Join Date
    Sep 2021
    Location
    Bridgwater, Somerset
    Posts
    87
    Great post guys, Just solved my battery warning light problem, which use to work until I changed it for the car builders LED type.
    Then it just stayed on all the time.
    Drove me nuts trying to work out why, then I found your post, which makes total sense on, no current to excite the alternator on start up.
    Refitted the old type 12v lamp with the new LED and hey presto its back working as it should, just tied the old 12v lamp up out of the way.
    Many thanks
    Mike
    Happy motoring, life`s to short to not get out and drive your cobra.

    AK Gen 2 LS3 6.2

    Regards
    Mike H

  9. #9
    Brilliant thread. Buying a cheap bulb to do the same and tuck it up out the way,
    Thank you
    Russ
    Russ

    www.russhowell.com
    AK Cobra - LS3

  10. #10
    Join Date
    Nov 2007
    Location
    Chester
    Posts
    706
    In line diode, never had a problem

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