Pecky's Vauxhall Decoder

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  1. #1
    Member leeumdee's Avatar
    Join Date
    Oct 2016
    Crewe, Cheshire
    Astra Mk5 1.6

    LED Wiring - On all the time but dim with headlights

    Hi guys,

    I'm installing LED backlights to my gauge pods. Currently I've got them wired up to ignition live and it works great apart from at night when they are too bright and distracting.

    I would like them to act like my instrument lights. Like the MFD screen, lit up all the time so I can see them in the day but when the headlights come on they dim slightly. It would also be nice to be able to adjust the brightness with the instrument dimmer switch. I'm just wondering is this even possible and if so, how? Can I tap into the wiring loom for the mfd screen? I'm guessing probe random wires of the loom looking for 12v and then a drop in volts when headlights are on? It's just I dont want to go poking around with a multimeter if it's not even doable.


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    • #2
      Member Bolter99's Avatar
      Join Date
      May 2015
      Cardiff,South Wales
      Insignia SRi NAV VXL Red CDTI
      I'm pretty sure the brightness is controlled via GM LAN/CANBUS, as there's a value for brightness in the Test Mode screen. If it was just a binary input (on or off via a wire) you'd be laughing.

      You could do something clunky with some relays, a normally closed relay with 12v from the headlights to the coil, switching between a 12v ignition live and a lower voltage.

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