Skip to content
View in the app

A better way to browse. Learn more.
Ford Owners Club - Ford Forums

A full-screen app on your home screen with push notifications, badges and more.

To install this app on iOS and iPadOS
  1. Tap the Share icon in Safari
  2. Scroll the menu and tap Add to Home Screen.
  3. Tap Add in the top-right corner.
To install this app on Android
  1. Tap the 3-dot menu (⋮) in the top-right corner of the browser.
  2. Tap Add to Home screen or Install app.
  3. Confirm by tapping Install.



Join the Independent Ford Owners' Club

Our community has been built by enthusiasts, for enthusiasts, and proudly run by Ford owners' for over 18 years. As an independent, non-official club, everything you’ll find here, advice, support, and opinions, comes directly from members with genuine Ford ownership experience.

Join our friendly community... it's Free!

 

Intermittent 12v charging issue

Ian Kershaw
Ian Kershaw
in Ford S-Max Club

Featured Replies

Hi,

I have had my S-Max for 4 years. I intermittently get a 12v Charging System Fault. The battery light will stay on for a few minutes then go off again. It has happened a few times and it can be months and months in-between occurring. I've checked the battery, connections and wiring. My local mechanic has checked the voltage pulling and it's fine. Any help and guidance gratefully appreciated.

Thanks.

  • Quote


    I'd say carry Forscan on your phone or laptop and a lead or dongle in the car to be prepared. When it happens, read any codes. 

    Otherwise in more depth I can only suggest a thorough check of integrity of all wiring and earthing of alternator and signals from the LIN bus system, including the use of an oscilloscope (although it sounds like you have done some of that)

    As a result of Low Battery alerts, I have a USB charger with a voltage display permanently mounted and visible 

    Intermittent faults are difficult but at least it doesn't cause an immediate failure.

  • Quote
    On 5/9/2025 at 8:05 PM, Ian Kershaw said:

    Hi,

     

    I have had my S-Max for 4 years. I intermittently get a 12v Charging System Fault. The battery light will stay on for a few minutes then go off again. It has happened a few times and it can be months and months in-between occurring. I've checked the battery, connections and wiring. My local mechanic has checked the voltage pulling and it's fine. Any help and guidance gratefully appreciated.

     

    Thanks.

     

  • Quote
    On 5/9/2025 at 8:31 PM, unofix said:

    Possible problem with the smart charge plug on the alternator. Check it is fully seated and that there is no damage or corrosion to the wires.

     

  • Quote
    8 hours ago, Ian Kershaw said:

    Hi,

    Thanks for the reply. Is this what I'm looking for.

    PXL_20250510_113952410.MP.jpg

    PXL_20250510_114000894.MP.jpg

     

  • Quote
    8 hours ago, unofix said:

    It certainly is.

    Unplug it and have a good look at the connections. Check for any signs of water damage/corrosion. Check the wire as it enters the back of the connector, they often suffer insulation damage.

     

  • Quote
    7 hours ago, unofix said:

    Just  spotted the greenish signs of corrosion on one of the photos

    connector.JPG

     

  • Quote

    • Latest Deals

    Ford UK Shop for genuine Ford parts & accessories

    Disclaimer: As the club is an eBay Partner, The club may be compensated if you make a purchase via the club

    Join the conversation

    You can post now and register later. If you have an account, sign in now to post with your account.

    Guest
    Reply to this topic...
    Go to topic listing

    The "Digestive"

    • The Digestive Forum Roundup (24th May - 31st May 2026)

      Steve ·
      The Digestive Forum Roundup (24th May - 31st May 2026) We hope this email finds you well and enjoying your week. As always, our forum has been buzzing with activity, so we’ve compiled the highlights for you. Plenty of interesting discussions are taking place, especially around the Ford Focus and Fiesta models. Starting off with the Focus, many members have been discussing issues with the Emergency Call System, particularly in the Mk4 model. PLB raised concerns about persistent malfunctions, a se
      Steve
      Steve
      • 163 views





    Background Picker
    Customize Layout

    Account

    Navigation

    Search

    Search

    Configure browser push notifications
    Chrome (Android)
    1. Tap the lock icon next to the address bar.
    2. Tap Permissions → Notifications.
    3. Adjust your preference.
    Chrome (Desktop)
    1. Click the padlock icon in the address bar.
    2. Select Site settings.
    3. Find Notifications and adjust your preference.