2003 B6 S4 - Car won't even turn over..

[Adamantium]

Went to the shops this afternoon (5min drive) everything normal.

Came back to the car, started her up and could hear what sounded like an engine fan on full blast?! (strange whirring noise) nothing unusual being report on the dash, no warning lights etc..
I drove her the short distance home, and within about 2mins of driving the strange noise became intermittant (and i noticed the battery light flickered on and off a few times at this point) and then the strange noise stopped entirely and seemingly everything went back to normal. (car drove and felt completely normal).

I parked up at home, switched off the ignition and popped the bonnet to see if anything obvious was amiss.. Having checked the engine bay - everything looked normal, so i decided i would start her up with the bonnet open to see if the strange sound was gonna start again... However when i turn the key in the ignition, I get nothing whatsoever. All the normal dash lights come on, I get the green "Ok" symbol, but nothing whatsoever from the engine.

My car does suffer from the common starter motor solinoid issue found on many B6 S4's (i.e. car can sometimes take 2min-45min to start when really cold), however it's 20 odd degrees celcius out there and the engine was obviously up to full temps having only just driven it.

I've left it for a couple of hours to cool down and tried again (although temp guage still showing about 1/4th temp) but it is still doing nothing at all.

Having searched on the subject, i've not found very much to suggest what the problem could be, some suggestions that symptoms like this could point to a faulty / broken Camshaft Position Sensor?

Any ideas / help would be greatly appreciated.
Thanks.
Adam.

[hlbeckley]

Change battery and starter motor
Had same issue

[Silverfox42]

I had a failed battery cell on my 05 B6 S4 which provided enough power to show ignition lights etc and no faults, but not enough to turn the starter motor. The battery showed 10.8 volts. This was a morning/cold start, and the damaged cell was blackened and dry.

Not sure about the whirring noise, so agree there may be something alternator or starter motor related.