Strange alternator behaviour!

[domiles1]

Or maybe there is a rational explanation! My alternator light is OFF during normal driving thus indicating that the alternator is charging my battery - but when the engine revs get higher, the light begins to glow! I first noticed this when I was going along the motorway at about 60mph, the light glowing at about 50% brightness indicating, I presume, that the alternator is not putting out its full battery-charging ability. The light will also glow as I get the engine up to high revs during A and B road driving. As the revs get higher, the alternator light begins to come on. I would have thought that the alternator would dish out MORE charge at higher revs, not less!...... Can anyone explain or advise as to what might be wrong?
(Its a 1985 1600 diesel, by the way).
Thanks,
Dom.

[Mocki]

this would indecate it's time for a brushpack change. the regulator is included in the brushpack........

it s a myth that alternators put out more the faster you rev the engine, infact, once you have reached the required revs, they do tend to drop out put a tad due to the regulator doing its job........ if you need to rev to get the correct output, there is something wrong.......... its NOT a dynamo...

[lhd]

Also check the part No. as there are two types.
My 83 diesel just would not work on a JK or GSF one, yet GSF assured me it was the correct one and even gave me a replacement thinking it was faulty.
ie fifty pence piece bit on the top.

I had to get one from VW at £30.00.
The paart No. for mine is...
070 903 803a.
If yourpart number is (not) the same as this you should be ok with the JK, GSF ones.....
hope this helps..........
lhd.................

[Ivorblueun]

just had this very same problem as mocki say's replace the brush/diode pack , turned out that one brush had all but disintigrated and tother wasn't much better, worth cleaning up the slip rings and contacts with some crocus or very fine emery paper before fitting new brushes.