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Thread: Focus st3 mk2 08 weird electrical outs

  1. #1
    Join Date
    Jun 2019
    Posts
    2

    Default Focus st3 mk2 08 weird electrical outs

    Hi guys
    I started my car the other morning and noticed bonnet open message, temp gauge blank and frost symbol highlighted. I also have random things not working since. windows/mirrors/heated seats/climate control fan (heater air con etc working)
    Ive checked fuses, mega fuses all ok, was advised battery might of gone bad causing all this, its allways started well. Ive tested voltage and its just under 12v off. Would it be worth getting a new battery to try? Mine is atleast nearly 3 years old. Is battery likey cause?
    Thanks

  2. #2
    Join Date
    May 2008
    Posts
    11,941

    Default

    In the morning when you come to your car you ideally need 12.6v i.e. to be showing 6 cells at 2.1v each. If you are getting a reading at 12v or less then the battery is either tired or you have a parasitic drain. When you start the car this voltage will drop and if it goes down to around 8-9v then there will be voltage 'starvation' for non essential circuits. Perhaps this is the problem.

    The charge system is Ford Smart Charge so you can get charging readings of well over 15v. Have you checked to see what it is charging at, all electrics off idling warm? Because of this higher than normal charge rate you must fit a silver calcium one as a normal lead acid one won't take it for long.
    I use Tayna for all my batteries. Fast delivery too. https://www.tayna.co.uk/
    Last edited by Hometune; 11-06-19 at 16:11.

  3. #3
    Join Date
    Jun 2019
    Posts
    2

    Default

    Great info, i will grab a battery from tayna pretty reasonable too!
    that makes alot of sense, would a voltage starvation cause the non essential electrics to not work during ignition before starting the car?
    I will check the battery voltage when running when i can
    Thanks!

  4. #4
    Join Date
    May 2008
    Posts
    11,941

    Default

    There are effectively 3 levels of 'importance' in how the car shares the electric power. The general electrical module (GEM in Ford speak) is responsible for this. Level one is the starter and engine ecu and other essential circuits followed by level two with the airbags, ABS, etc and lastly the non essentials like the radio and minor circuits.
    Very often on many makes the airbag light will come on if the voltage drops too low and the fault code will tell you this. It will go off again once it gets its proper voltage but the fault code will remain in the memory until erased on diagnostic equipment.

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