Battery warning light on

nealefloyd

Member
Driving to work the other day the Battery warning light came on the dashboard.I was nearly late so had to carry on and just managed to get into a parking space with a push.The battery was drained so much I had to leave the car overnight and a neighbour gave me a jump start ,next day, after we waited for his car to charge mine sufficiently.
Now,I assume this is the Alternator at fault?Having had a look under the bonnet,the Alternator looks rather inaccessible.Just wondered if anyone has any advice or tips on how to remove it,to save time and grazed knuckles etc.Did a quick search here but couldn't find a "How To" for this particular job and it does look as if it's more complicated than your average car with the drive belt also going to the crankshaft!It's definitely not my battery as it was brand new only about a month ago.
Hoping someone can point me in the right direction as I'd prefer A2 power to pedals!!Thanks.
 
Had it been an FSI, I could have helped, but I'm sure a 1.4 minder will be along soon. Could edit the title to include:
"1.4 Petrol"
Mac.
 
If your car originally started fine and the battery light came up during your journey seems strange for the battery suddenly failing to such a degree. Not impossible, but unlikely.

The alternator has three areas that can fail without notice: brushes, rectifier and, if fitted, one way clutch.

If you have it again, put a voltmeter across the battery. It should be sitting above 12.5v roughly. Start the car, and if charging the volts should quickly climb to 13.5 or higher.

If you see no climbing above the background battery voltage, it's not charging. You could have a quick look at the main output lead from the alternator, on off-chance it's loose but odds are the alternator has failed in some way. If you're practical and the alternator is a Bosch, you may elect to follow one of the numerous YouTubes on testing and fixing it and just replace the failed part: all parts are available from eBay. I only suggest this as a repaired Bosch is a better long term bet than a cheap semi branded new one. Best option is a like for like replacement of course.

Generally though, if you hand-spin alternator on a board / table / workbench (soundboard) and it has no noticeable bearing noise, you can DiY repair it

As a wider point for anyone looking at this thread, if you ever need to remove a one way clutch from an alternator, buy the spline tool (ebay) and buzz the pulley off with an impact gun: don't try and use the inner spline / Torx to counter hold the pulley: it's nearly impossible and you'll just break tools or yourself. A quick burst with a gun will remove it immediately.

Hopefully the new battery will have cured it, but perhaps have in back of your mind there might be another chapter to follow :)
 
Two possibilities I can think of.

1) earthing issue - maybe the main starter one behind the headlight. If that is needing to be cleaned even a fresh battery struggles to start the car.
2) alternator (or part thereof) knackered. Workshop manual diagram to remove it for the 1.4i excerpted below. From not being able to remove alternator on my Tdi, I can suggest soaking the threaded ends of the bolts holding the alternator on with penetrating fluid for a while before you try to shift them - one of mine snapped off and the mechanic ended up having to remove the alternator in halves with a plasma cutter.
 

Attachments

  • Alternator work.pdf
    966.9 KB · Views: 208
Most likely, the regulator/brush unit has failed. Find out from the option codes what the amperage of your alternator is and then get the correct replacement. Remove the alternator and then replace the unit - easy to do, no special tools required. Search Youtube for guides.


Disconnect the negative post of the battery before you start!

RAB
 
Last edited by a moderator:
Most likely, the regulator/brush unit has failed. Find out from the option codes what the amperage of your alternator is and then get the correct replacement. Remove the alternator and then replace the unit - easy to do, no special tools required. Search Youtube for guides.


Disconnect the negative post of the battery before you start!

RAB
Thanks very much,Rab,really appreciated.
 
Two possibilities I can think of.

1) earthing issue - maybe the main starter one behind the headlight. If that is needing to be cleaned even a fresh battery struggles to start the car.
2) alternator (or part thereof) knackered. Workshop manual diagram to remove it for the 1.4i excerpted below. From not being able to remove alternator on my Tdi, I can suggest soaking the threaded ends of the bolts holding the alternator on with penetrating fluid for a while before you try to shift them - one of mine snapped off and the mechanic ended up having to remove the alternator in halves with a plasma cutter.
Thank you so much,Robin.This is exactly what I was after and will help enormously time wise.Got a replacement alternator coming tomorrow.Let you know how I get on.
 
Just to update everyone on the problem I was having.Ordered a replacement alternator from Ebay and did the swap over this morning.Everything came apart reasonably easy and likewise back together,the only problem being getting enough slack on the belt tensioner to refit the belt.Found it easier to jack up the car and lever from underneath.Was a little apprehensive on starting up but NO battery warning light or any others.So,well pleased with myself!I'd like to thank everyone who took the time to post me the diagrams and videos,saved me time and money.This club is by far and away the most helpful I've ever been in.THANKS!!!
 
Just to update everyone on the problem I was having.Ordered a replacement alternator from Ebay and did the swap over this morning.Everything came apart reasonably easy and likewise back together,the only problem being getting enough slack on the belt tensioner to refit the belt.Found it easier to jack up the car and lever from underneath.Was a little apprehensive on starting up but NO battery warning light or any others.So,well pleased with myself!I'd like to thank everyone who took the time to post me the diagrams and videos,saved me time and money.This club is by far and away the most helpful I've ever been in.THANKS!!!
p.s will probably repair my old 1 as a spare.
 
Back
Top