V6 Engine Problem

V6 Engine Problem

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ukflyboy

Original Poster:

246 posts

115 months

Monday 20th April 2015
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Having the alternator refurbed certainly won't have done the car any harm and I'm optimistcally hopeful that in the process of messing around with wires and stuff that I may accidentally have sorted things. But I really won't know until it is refitted, probably Wednesday night.

Removing it has still been a very worthwhile step in diagnosing the issue and there are a few options for isolating where the problem might be...

mk1fan

10,507 posts

224 months

Monday 20th April 2015
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If you have time consider swapping the rubbish alternator adjuster arm arrangement for rose joints and a turnbckle.

TVRees

1,080 posts

111 months

Monday 20th April 2015
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ukflyboy said:
... and voltage regulator a bit worn
That's not good - are you considering replacing it ?

At the point where you had the engine cut out, the alternator stator output voltage rises above the battery voltage and the warning lamp will go out. Then at this time the main diodes will "open" so current flows to the battery and it commences charging. Maybe one (or more) of these diodes is also defective and you are not getting a good DC rectified voltage. I would recommend to include a new diode pack as part of the alternator overhaul.


ukflyboy

Original Poster:

246 posts

115 months

Monday 20th April 2015
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The alternator is with a pro in Burghfield who comes highly recommended and only deals with starters and alternators, so I'd hope his testing and repairs will cover any diode problems. I'll mention it specifically when I hear from him tomorrow though. And yes, he is gonna replace the regulator, the bearings and anything else that looks like it might need sorted when he strips it completely apart. To answer a few earlier questions, yes I've tested all the blade fuses (no idea how to test the big clusters or what on earth they are though!), nope, I've not touched a thing between parking it up after my delivery and trying it again the other night when I discovered the problem. Not had anything in the cigarette lighter.
Ticked it over again tonight for 20 seconds without the alternator in to make sure my previous fault isolation wasn't a fluke and it started and ran above 3000 rpm effortlessly (sounded great too!). I'll stick the alternator back in, hopefully Wednesday and see how I get on. If the fault is still there the alternator repair guy suggested running a jumper lead off the alternator earth to the battery so I'll discuss that with him in more detail when I pick it up.

How many and where are the main earths on a late S3?

mep12345

2,061 posts

200 months

Monday 20th April 2015
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Pete,

Earths are battery to chassis, engine to diagonal front chassis member (drivers side iirc) stater motor to chassis(passenger side) and in rear left wheel arch - petrol tank to chassis

The battery and engine to chassis are the main ones, I used to remove and clean them each winter as they do build up corrosion products. I hadn't got to doing them this year so definitely worth doing either way

Mark

ukflyboy

Original Poster:

246 posts

115 months

Wednesday 22nd April 2015
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Well I am happy to report that after sticking the as-new alternator on this evening the S fired up and ran beautifully on a 45 minute jolly around the countryside tonight! I assume it was the alty that did the trick but I cleaned all the earths etc while it was off too, so I'll never really know.

But the important thing is that it is up and running again and I couldnt have done it without all your help, so many thanks!! Have to say, the guy at Burghfield did a cracking job on the alternator too, really good service and highly recommended.

v8s4me

7,234 posts

218 months

Thursday 23rd April 2015
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There you are, that was easy wasn't it? thumbup Enjoy thumbup

mep12345

2,061 posts

200 months

Thursday 23rd April 2015
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Glad it's sorted. YHM wrt your other questions

Niiige

640 posts

168 months

Thursday 23rd April 2015
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Glad to hear you are sorted - look forward to seeing you at SCH !