On Tue, 3 Dec 2002, David Brodbeck wrote:

> My diesel is that way.  I've never noticed it in any other car, but I kind
> of suspect that's because my gas cars all have a high idle when cold.  The
> diesel only has one idle speed.  Then again, my alternator is also full of
> oil thanks to the PO, so that may have something to do with it. ;)
> Charges fine once it's been revved once, though.  I think there just isn't
> enough power to energize the field coil below a certain speed -- until
> that happens it's working on residual magnetism and the output is really
> low.

As I had come to understand it, there's a cutoff on alternators (either by
design or by nature) that effectively disables charging at RPMs below idle
(i.e. during starting.)  I had an Audi coupe in which the PO had creatively
installed an alternator from a Mazda RX-7 (hint: it involved brutal removal
of the power steering), and while the battery light wouldn't come on, the
voltage would slowly drop to nothing.  Blip the throttle up to 1400rpm or
so, and it'd jump to 14V and stay put.

I still have that coupe, sorta.. if I ever do an I5 conversion on the bus
with it, it's going to get the Blade Runner dash gauges too. :)

ian Butler / ian@hplx.net
'88 Scirocco 16v, '87 Syncro GL
(plus remaining bits and pieces of an '86 Audi CGT)