Battery light problem

[Lipman1973]

I'm hoping someone can help me.  I have an 11 plate SMax 2.2 Titanium Auto, it's only done 40k and the battery light has come on for the past four or so days.  I have had the battery tested and the charging and both appear to be fine.  The car starts fine every time and has run with significant load for an extended period so I am sure that the battery is being recharged and holding it.  Can anyone help as I am reluctant to take this to a main dealer to be told I need to spend hundreds. Cheers

[Chrispb]

Hello and 
What I would try is disconnecting the small thin wire from the alternator, if the light goes out then I would say the fault is likely with the alternator

[drcotts]

Might be wirth putting a voltmeter across the battery and seeing what voltage you get.
Should ideally be 13.5 volts or more.
If its less say like 12.7 then this is too low.

[gregers]

 
you can check the battery voltage using the on board diagnostic check.

[Lipman1973]

Right, firstly sorry for the delay in replying, i've been snowed under with work and not had a chance to follow up on your advice.  Now I'm no mechanic but here's what I know now.  I have checked the on-board faults and there is nothing logged, no DTC codes.

From cold, checking the battery with a basic meter it shows about 13.2 engine running loaded read 13.6/7 after 2 minutes of the engine running the battery light comes on, stopped engine reading 12.6 and restart fine as always.

Looked for the thin wire?? cant really make a wire out from the Alternator only on the + terminal there are two main connections and a single red wire.  I removed the red wire and went through the same process and all happened the same and after a few moments the batter light still came on, just not sure if this was the correct single thin wire that I was advised to remove.

Thanks for your help so far and as if I haven't got enough problem my other car a focus has also got a electrical problem...

[Lipman1973]

Right, just had the AA in attendance re my other Focus issue and we chatted about the S-Max and his advice was stick a piece of tape over the light.  The Alternator is charging clearly and the battery retaining its charge so carry on as we normally do.  The only issue being that is I do get a problem with it I won't realise until the battery is flat and it wont start or it dies whilst out one day.

Not really sure what else I can do so would appreciate any thoughts, views, if you agree with this course of action or is this might cause other problems by ignoring it, answers on a postcard please.  Thanks again

[Chrispb]

Don't know if this will help, below is a view of the rear of my alternator.
You can clearly see the two wires, was trying to rule out whether you have a dodgy alternator or other wiring problem or instrument cluster
[attachimg=1]

[Mirez]

Not forgetting the new MoT rules though, all warning lights must be off so it will fail if you do that ;(

[Lipman1973]

So sorry if I am being dim, if I disconnect the warning light wire as shown in the photo, the light should go out right? what will this prove, that it's due to the alternator and I need to replace this even though its working and chanrges as required?? what exactly does it prove and why does it rule out the cluster etc?

If the light goes out if the wire is removed, would this be spotted on an MOT? (sure I know the answer to this question already).

Thanks

[Grant2012]

mot rule says the light must come on and then go off --- nothing more 

[Chrispb]

Am only suggesting disconnecting for the purpose off seeing if the light stays off when engines running, if it does stay off then you know the alternator is putting it on for whatever reason.