Hello All,

 

After a bit of advice here please, my neighbour has 2013 1.6 tdi, she tells me for a while the battery light has been on very very faintly, you could only see it in the dark with the lights off but it has started without fail even in -5 degree frost, yesterday the light came on really bright and the battery is not charging at all. Taken a good look at it, followed the two wires that plug into the top of the alternator and looked for breaks in the places I have read they happen and checked the fuses for hairline cracks but couldn't find anything, I put a volt meter on the plug to alternator and have 12V so have to assume the alternator is getting enough to energise. Odd thing is when you first start it the battery light goes out when it starts, as soon as you try to move it comes on, when I started it last and the light was out put a volt meter on the battery and it seemed to be reading 13 volts then dropped back down to the original battery voltage before I started it and the light had illuminated.  Thinking it has to be the alternator but just wondered if anybody has experienced this before I go ahead and swap it.

 

Thanks in advance

Output from the alternator with voltage read across the battery terminals should be 14.4V with engine running.

 

Nothing else is acceptable.

16 minutes ago, Lezley said:

the battery light has been on very very faintly, you could only see it in the dark with the lights off but it has started without fail even in -5 degree frost, yesterday the light came on really bright and the battery is not charging

Hey Lezley, thanks for the clear history. That really helps.

 

I think your neighbour has one or more failed diodes in the rectifier part of the alternator. My recommendation would be that they contact a good local garage or independent VAG specialist, or an auto electrician if there is one in your area, to confirm the diagnosis, and get a decent price on the replacement.

Thanks you both for the reply, that was the conclusion I had come to but just wanted to make sure I had checked everything before proceeding.

Remember you can simply replace the voltage regulator part of the alternator, no need to change the whole unit as often there is nothing wrong with the mechanical part.

A far cheaper option.

17 minutes ago, UrbanPanzer said:

you can simply replace the voltage regulator part of the alternator, no need to change the whole unit

Fairly sure that depends on the make of alternator (not stated).

Have yet to find an alternator where you cannot replace the actual bit that usually fails.

 

Looking at the manual, it's either a Bosch or Valeo unit.

 

So one of 2 numbers of regulator, both available on Ebay for example. They are clearly marked on the back of the alternator, so a quick look should show either Bosch or Valeo.