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D2 - Engine Bay Everything under the bonnet

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Old 20th March 2021, 06:19 PM
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Default Alternator confusion

Hello

So my alternator went bad so I ordered a replacement regulator I found a nasty suprise inside the casing

Someone has ( I think) snapped off the bolt that holds the regulator and drilled another one slightly off OR bought the wrong regulator so drilled a hole to fit it.

It's an HC-Cargo 138310 regulator which apparently corresponds to vag part numbers: 046903015F, 059903015 and 078903016.

The Hella regulator I purchased corresponds to part number 028 903 803D from this thread: http://forum.a8parts.co.uk/showthread.php?t=16044.

So the question is: Is the original regulator found wrong one and the one I purchased is correct? and having that damaged/wrong thread hole it probably writes the whole alternator off. Since I have 2 new bearings and a regulator I'm probably best off buying a used 2.8 QS alternator from forum sponsors and putting those new parts on it?
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Old 21st March 2021, 08:21 PM
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Looking for a new alternator now... this one couldn't be salvadged due to cracks in threads/casing.

Google is telling me 8 903 016 is a part number for a 150A Bosch alternator for a 6 cyl. petrol engine but I can't find any.

Help!
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Old 21st March 2021, 09:22 PM
MikkiJayne MikkiJayne is offline
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078 903 016
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Old 23rd March 2021, 11:52 AM
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Thanks Mikki! ordered one for 34.99 with next day postage.. mad. It even came with the missing plug,
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Old 23rd March 2021, 12:54 PM
MikkiJayne MikkiJayne is offline
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That red wire with the white connector is for the starter solenoid. Only the 3.7 uses that spade terminal on the alternator - not entirely sure why but I think it may turn it off under load to save fuel.
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Old 23rd March 2021, 01:17 PM
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Ahh, that explains why it was missing on my 2,8 to begin with. I've also noticed im missing the whole air duct thing that connects to the pipe thing on the rear :O

Superior knowledge coming from you as always
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Old 9th April 2021, 06:48 PM
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I've gotten to the bottom of the issue. It was the alternator clutch allowing slippage in both(!) directions..

Why does the 2.8 have it and 4.2 or 3.7 don't? It just seems like an unnecessary complication.
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Old 10th April 2021, 04:37 PM
Nick Jones Nick Jones is offline
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Dunno why are a thing on VAG stuff at all. Must be something odd about the way they design their harmonic dampers or something. I can tell you that when they are seized solid on 4 cylinder diesel cars it produces a whole host of of strange and unpleasant symptoms. My son has a B6 A4 1.9TDi that was previously my brothers and that came to us with a long history of "power steering problems" It's had several belts, a tensioner, a fluid change and flush and a recon PAS pump (mis-sold as new!). Still it would squeal and screech when manoeuvring with a most disconcerting pulsing and kicking the back through the steering. Strangely enough, 30 seconds on google told me this would be the one way clutch on the alternator seized in both directions (gave me a WTF moment as it was news to me such things even existed!), but it proved to be true and fitting a new one (much harder than writing this), transformed the car.

I know the one on my 2.8 has gone the same way, though the symptoms are slight enough to ignore and also the one on Senior Managements TT, also with minor symptoms. I'm ignoring them. The TT in particular looks like a complete sod to deal with.

Suspect the V8s don't have them as the power strokes overlap sufficiently to render them completely pointless rather than just moderately pointless as on the V6 and petrol 4 pots.

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Old 10th April 2021, 04:52 PM
MikkiJayne MikkiJayne is offline
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They originated on the 1.9 rotary pump diesels. The torque pulses from the crank, combined with the rotational intertia of the alternator combined to unscrew the crank sprocket bolt The resulting effect (crank sprocket falling off) destroyed many engines before someone figured out what was happening. In VAG stuff the clutched pulley turned up in the 90hp TDI engine I believe and then became ubiquitous on diesels, spread to petrol engines, and now appears to be on almost everything.

It may be a refinement thing in the D2 V6, as the A4 with the same engine doesn't have it.
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Old 11th April 2021, 09:02 PM
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thanks for the above comments. I decided to invest in a brand new INA clutch, even if its just for the refinement, thats what A8 is all about.
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