Hi all,

On my focus diesel 1.8 red battery light is now on. Changed battery but light staying on. Battery has 12.6v without engine on, 14.2v with engine ticking over, belt is in place an alternator is turning. I am at a loss and trying to avoid the garage if possible.any help is appreciated. I have read ways to reset the light but cannot get these to work

 

20 minutes ago, Dragonmaster said:

Hi all,

On my focus diesel 1.8 red battery light is now on. Changed battery but light staying on. Battery has 12.6v without engine on, 14.2v with engine ticking over, belt is in place an alternator is turning. I am at a loss and trying to avoid the garage if possible.any help is appreciated. I have read ways to reset the light but cannot get these to work

 

You may need to reset the BCM

https://www.vehiclehistory.com/questions/what-is-the-ford-focus-reset-procedure-after-battery-change-133521

My brother had 2008 1.8 diesel estate. Alternator was turning but not fast enough. The pulley has a one way clutch in it. The pulley clutch had failed so there was a lot of slip in it. I am not saying this is your problem but it is something that can catch you out. My brother bought a replacement alternator and it was only when  starting to fit it we found the pulley problem(for anyone reading this who does not know this engine, the alternator does not come with pulley, the pulley and shaft are a separate part from the alternator on this engine)
 

22 hours ago, isetta said:

My brother had 2008 1.8 diesel estate. Alternator was turning but not fast enough. The pulley has a one way clutch in it. The pulley clutch had failed so there was a lot of slip in it. I am not saying this is your problem but it is something that can catch you out. My brother bought a replacement alternator and it was only when  starting to fit it we found the pulley problem(for anyone reading this who does not know this engine, the alternator does not come with pulley, the pulley and shaft are a separate part from the alternator on this engine)
 

How easy is this to change. Thanks

Not very easy. Jack up, remove  the undertray. Take drivers side wheel off, remove wheel arch liner. Take tension off the belt tensioner, done by ***** a bolt in a threaded hole but not much space to move spanner. Once the belt is off there are three bolts holding shaft on the holder, bolt heads close to pulley. And three bolts holding the other end of shaft to alternator, Turn shaft the get to each one in turn. 

To test the pulley clutch can you get your hand onto the shaft between pulley and alternator. Try turning it , it should go one way and not the other. It’s a bit of work to go to if you’re not sure it’s faulty. All my comments assume yours is same as my brothers 2008 1.8tdci but I don’t know if / when there were revisions.   Obviously support car properly when raised, don’t just rely on the jack.

I would definitely try a BCM reset first, you can do this sitting on your ars* in the drivers seat out of the rain! LOL 😁

10 minutes ago, StephenFord said:

I would definitely try a BCM reset first, you can do this sitting on your ars* in the drivers seat out of the rain! LOL 😁

As all the headlights and fog lights are on a turny type switch how do you press the fog light for the BCM reset. The link you gave appears to be for a mk 3. Thanks much appreciated

5 minutes ago, Dragonmaster said:

As all the headlights and fog lights are on a turny type switch how do you press the fog light for the BCM reset. The link you gave appears to be for a mk 3. Thanks much appreciated

Apologies buddy, just realised you have a 2008 car, I'm unsure if the 'battery control module' is actually fitted to your car! (It's not on my 2005 model) It's a device about the size of a box of matches attached to the positive battery lead. If you don't have one, just ignore my previous erroneous posts, sorry...

Ok thanks can't say I've seen one but will have a look tomorrow

I've turned up late to the party on this ... Doh !!

Just to clear a few little things first when @StephenFord refers to resetting the 'BCM' (Body Control Module) he actually means the 'BMS' (Battery Monitor System), but I'll let him off .... it's his age you know 🤣

Next since you have a 2008 Focus it was made before the days of the BMS so on your car there is nothing to re-set.

You do have an alternator with a 'Smart Charge' system. From the fact your battery voltage is jumping from 12.6V up to 14.2V your alternators smart charge system is not working correctly. When the system fails it defaults to being a normal alternator and charges at 14.2V regardless of the demand or battery requirement.

If you look on the side of your alternator, near the back you will find a small plug connector - this is the smart control. If you unplug the connector you may find it has corroded or one of the 3 wires to it has broken. The alternator will continue to work but it will eventually damage your battery by overcharging.

Take a good look at the smart connector and wires, if they look to be in good condition then you may have a faulty alternator.

19 hours ago, unofix said:

I've turned up late to the party on this ... Doh !!

Just to clear a few little things first when @StephenFord refers to resetting the 'BCM' (Body Control Module) he actually means the 'BMS' (Battery Monitor System), but I'll let him off .... it's his age you know 🤣

Next since you have a 2008 Focus it was made before the days of the BMS so on your car there is nothing to re-set.

You do have an alternator with a 'Smart Charge' system. From the fact your battery voltage is jumping from 12.6V up to 14.2V your alternators smart charge system is not working correctly. When the system fails it defaults to being a normal alternator and charges at 14.2V regardless of the demand or battery requirement.

If you look on the side of your alternator, near the back you will find a small plug connector - this is the smart control. If you unplug the connector you may find it has corroded or one of the 3 wires to it has broken. The alternator will continue to work but it will eventually damage your battery by overcharging.

Take a good look at the smart connector and wires, if they look to be in good condition then you may have a faulty alternator.

Thanks will have a look at it in daylight. I suspect it may be the smart charge or the pulley on the front of the alternator. It won't be simple that's for sure.

21 hours ago, Dragonmaster said:

Thanks will have a look at it in daylight. I suspect it may be the smart charge or the pulley on the front of the alternator. It won't be simple that's for sure.

How do I check the smart charge. I can see it but not sure what I'm looking for thanks again

On 11/20/2021 at 12:09 AM, unofix said:

If you unplug the connector you may find it has corroded or one of the 3 wires to it has broken.

You have to unplug the connector.

Check the alternator and the connector for signs of greenish corrosion on the pins. Check that the wires going to the plug are in good condition, give them a pull and make sure they are still connected to the plug.

You can't easily test the smart charge controller on the alternator so if you suspect that it may have failed then get a service exchange alternator unit from a repair specialist should cost about £90