alternator not charging

**tbs** · 12-09-2011,11:03 AM

hi guys any ideas what could be the problem the alternator is nt charging but when it was taken off and repleced with a working same issue no charging then i go tthem both tested and the alternators work but dont charge the battery any suggestions would be helpful ?

**Lofty79** · 12-09-2011,11:14 AM

check the earthing points arent corroded, and that it is attached to body and to ground, then check the powerline to the battery, and any other earth points straps or whatever the engine uses.

It is also likely to be alternator relay.

try wiring first as thats just time, drawing a blank then try testing to alternator relay.

my guess would be more likely a 1: corroded battery negative terminal, 2: chassis ground dodgy 3: alternator wiring and ground, 4: alternator relay, 5: fuse related to alternator.

Hope that helps

**jimma04** · 17-09-2011,03:28 PM

Do you have a batt light with ignition on non running ???

**tbs** · 20-09-2011,12:18 PM

no it didnt apparently the alternator is fine and the voltage regulator i have cheked the wire from battery to alternator and that pushes through current fine i just don know what else it could be and theres not many good mechanics around where i live

**batteryman** · 21-09-2011,12:55 PM

Sounds silly but does your battery charge off the car? Dud battery can give you all sorts of odd problems.

**tbs** · 21-09-2011,04:36 PM

no it dont sound silly but that the first thing i checked but i had a hunch it would definately be something to do with alternator itself chacked battery checked wiring to it opened up the alternator turns out to be the voltage regulator it should all be sorted now thank for your help guys

**Crasher** · 21-09-2011,05:30 PM

As asked above, does the alternator warning light in the instruments light up when you turn on the ignition BUT without the engine running?

**ChrisYates** · 09-10-2011,08:44 AM

Hi there,

I've only just come up against this problem. The battery icon warning light is on when the ignition is on and when the engine isn't running. Then, when I start the engine the battery icon warning light stays on, the volt meter appears to be a couple of volts lower than usual.

Thinking it was the battery (first cold morning of the year?) I took it in to halfords and one of their staff tested the battery with the engine off. He said it was ok. He then checked the alternator with his same diagnostic kit (with engine running) and it returned the message "regulator volts low".

One anomaly to this was soon after I set out to Halfords yesterday the voltage needle did jump back up to 14 volts and the battery warning light went off.

Should I follow the diagnostic process that Lofty79 recommends in the first instance?

1: corroded battery negative terminal, 2: chassis ground dodgy 3: alternator wiring and ground, 4: alternator relay, 5: fuse related to alternator.

many thanks

Chris

**Crasher** · 09-10-2011,01:15 PM

I would fit a quality reconditioned exchange alternator. Avoid cheap recons as the likelihood is that you will be pulling it back off again all too soon, sometimes just out of warranty. Genuine VAG exchange units are pricey but reliable and have a two year parts and labour warranty.

**ChrisYates** · 10-10-2011,02:07 PM

I've read some of the wiring schematic and there appears to be an "alternator cut-in relay" on the 13 point relay carrier. I've heard that most alternators have solid state control to avoid discharging the battery at low revs. However, I'd like to try this relay first. Only thing, can't find the critter!
Is it in the nest of relays behind the fuse panel (Right hand drive fuse panel adjacent to steering).