Battery Light Flashes when heavy throttle used

Hi, hoping someone can save my sanity!

Middle of last week, my A4 1.9TDi Sport Avant started showing me the battery light flashing when I went past about a third of the accelerator. Let off, goes out. If I tried ignoring it, suddenly all sorts of lights come on and I lose engine power.

Now, I checked the voltage, keeps between 14.2 and 14.4v. So I stripped all the plugs off, cleaned them, cleaned battery terminals, all the positive connections next to the battery, cleaned alternator mounting points to make sure the earth connection was good.
This made things slightly better, but did not solve the issue.

So, I changed the alternator pulley, slight play in the horizontal plane, but was not slipping or seized, I just assumed it may have been giving way under load. No.
So I then took it to an audi mechanic for a quick look, which resulted in me changing the tensioner, as this was kicking a bit, so maybe letting the belt slip under throttle.

Seemed good after doing it, but then car was cold. I took the car out today, after a few miles, light starts flashing when you go past about half way, worse if you are turning a corner etc.
There seems to be no difference if you turn all electrics off or have everything going as normal.
I've striped the regulator off the alternator, cleaned contacts, brushes seem really good.

I'm getting a belt tomorrow, but old one does not seem that bad, also there does not seem any screaming, or screeching that I'd normally associate with a slipping belt.

I'd love to say I'd down loaded fault codes, but my laptop with Vagcom is also ****** broken.

Any ideas, people had same issues, very very welcome!!

Engines the AVF 130 BHP 1.9

Thanks

Well, changd the belt and it has not changed anything.

I had a garage check the alternator with a battery load tester. Think I'll try putting my multimeter on it, take it for a drive and see the results.

Trying to find someone local, but if not, I'll just have to pay for it. Don't know if I'm chasing the wrong fault. Coming on tonight when going straight, not turning, so no extra strain on belt.

Thanks for replies though.

Well quick update, I managed to wedge my multimeter between the dash and windscreen, leads going straight to the battery terminals, 14.2-14.4v on idle, took car out for a drive, still 14.2-14.4v. Heavy throttle, light starts to come on, voltage drops to 13.5v, foot off, light out, back to 14.4v.

Took it easy, got back to the house, turned engine off, drops to 13.8v (as expected) and was pretty steady until I disconnected the leads. I'm hoping this indicates that the regulator is playing up, so I'll try getting one tomorrow.

Any other ideas very welcome mind! Or , if I could be cheeky, anyone with a spare 140 amp alternator around the bridgend area I could try on the car?

Sorry, have to try!

Belt tensioner is very stiff, lot harder to move than old one, not skipping and belt tensions seems good.

Well, after changing the regulator on the alternator, thought I'd solved the problem. Was behaving itself, prolonged use of full throttle, turning no issues.

On my way back from work today, lost all power, no electrics, engine cut everything gone, then turn key (whilst driving, fortunately no-one was behind me or there might be a different outcome) starts, runs bit rough, then clears and away to go. Then, get a flicker from the battery light.

Thought at this point maybe the battery terminal was not tight enough, or some other connection.

So, after getting home and sorting sons food etc, started to have a better look. Stripped all connections again, used multimeter to check continuity and resistance, no problems, so tightened all up. Thought I'd have a look for any loose earths, when moving the airbox produced a lovely big spark.

Turns out, the live battery cable to the starter motor was arcing to the chassis rail but only at certain moments. Hence it not showing up during measurements.

So, at present, it now wears a hose pipe to protect it until I have chance to put a more permanent repair in place.

Thanks for all the replies

Rob