I've just converted my beetle to an alternator and have a couple of questions. Test drove it yesterday, all perfect. Drove 12k to work this morning, no probs. Leaving work tonight, headlights on, the alternator light starts dimly glowing and the engine sounds whiny, like a siren in the far off distance. Pulled over to check, and it seems to be coming from the alternator zone, but only when I accelerate. Any ideas? Preferably a nice easy fix so I don't have to spend another weekend getting up close and personal with the engine bay :-)
Cheers,
Angela

alternator bearings I'd say

Could just be the fan scraping on the housing seeing that you've just had it apart.

Hmm, because the alternator light is glowing, assuming the blade plug at the alternator is still on it states that it isn't charging.

Fan scraping makes a horrible loud noise, but should be able to still charge and not get that light.

New alternators for vw's are a bit of a mine field when it comes to dodging crap. One i purchased didn't even come with a keyway machined in the shaft for the pulley, with the supplier stating its 'suppose' to be like that. Is it still under a warranty/guarantee?

Alternator is still under warranty (thankfully!), but I did buy a cheap one. Definitely not a horrible scraping sound, and I was very careful about the fan placement.
After searching a lot last night, I put an extra shim in the fan belt pulley this morning, because I think I had it a little snug. Not enough that it should have done any damage I hope, just not deflecting quite the full 1/2 inch.
Driving to work this morning, not much sound, just a very occasional whistle, and no glowing light. Will wait and see I suppose. I suppose if it is the bearings, then the sound will only get worse?

Over the years I've had scraping fans sound anything from a high pitch whistle through supercharger whine to horrible scraping. I'd check the fan first before you blame the alternator.

Thanks. I'll have another look at the fan gap.

Hi
Did you end up sourcing the problem?

brushes. check them. seen this happen few times when the brushes are just barely making electrical contact the windings in the rotor and/or stator resonate and make a whiny/whirly sound which increase with revs. Can be bearings but my finder is on the brushes since we have a dim glowing light as well.


if you want to test this, kill the ignition supply to the alternator and/or the B+ (depending on the design) to isolate it electrically, if the whine goes away its probably brushes if not, then its bearings or some other mechanical problem with it.