The other half phone me on her way home Tuesday to say she we losing electrical power on our D3 (2006 / Manual / SE), she was only 2 miles from home so managed to get in home and back on the drive.

Having had a look tuesday night it was showing a HDC fault on the dash but did start sluggishly with dimmed lights, so having had a google i am wondering if it could be the battery on the way out or alternator? It was the first cold day of the year on Tuesday and the battery is circa 5 years old. I put it on my Ctek as it only does short runs and the battery had a full charge.

Got my stepson to use his volt meter to check the alternator tonight and was consistent at 12 volts even after putting 2000 revs on and running for 5 minutes.

so now undecided if alternator or battery. Any thoughts or suggestions?

If it is the alternator will have a go at changing myself as having goggled it look not to complicated. Though I am no mechanic

Cheers
Matt

If you are only getting 12v at 2000 rpm then it looks like there may be a problem with the alternator. Check lead to battery in case that has come lose just in case though. Also check the belt isn't slipping.

Thanks for that assume to check the belt I just need to remove the fan cover start the engine and make sure the belt is turning ?

Probably should have have checked lead I’ll put a spanner in them tomorrow night and check there tigh

Thanks
Matt

Yes, you should be able to check the belt without removing the fan itself, just the cover. There is a belt tensioner that can fail and cause the belt to slip.

Stupid question how will I know if the belt tensioner had slipped

look at the belt tensioner when the engine is running. There should be very little, if any movement of the tensioner arm or pulley, also listen for any squeaks. If there is visible deflection of the pulley, arm or belt or there is a squeak from the pulley, the tensioner should be replaced.

Just use a multi meter on the battery terminals with the engine running. It should shos more than 13.6 volts at idle with the headlights on. If not then there's a charging issue, which needs sorting. It's been known for the alternator on the D3 to fail, sometimes short circuiting, causing the main cables to melt or worse.