Date:         05 Mar 96 16:35:00 EST
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         BOWMANR%em.EDW@localhost (Mr.Roger Bowman)
Subject:      Re: Headlight oddity


But that Chev alternator does have a few odd characteristics. When I
first start the engine, the alternator light stays on, and voltage at
the battery is rght around 11.5 to 12 volts-- obviously the alternator
isn't alternating, and the battery is discharging as it supplies current
for ignition, lites etc. When I rev the engine to about 3,000 rpm,
suddenly the alternator light goes out, the headlights bet brighter, etc.,
and system voltage now measures around 13.6V. After that, the system
operates correctly Seems to take a while to energize the alternator's
coil enough for it to bootstrap itself into producing electricity.

________________________________________________________________
This is, I beleive, a "feature"

GM, in whatever wisdom they happened to have laying around, designed some of 
their alternators to behave just as you described- delaying the start of the 
"charge" cycle for some short period of time.  I can't remember just why GM 
decided this was a good idea; likely had something to do with emissions from 
a "cold" engine.  In any case, test procedures for this series of 
alternators included "waiting" for some period of time (like, what....30 
seconds?) before measuring the charging voltage and deciding the alt was 
dead.  I suspect that the revving to 3,000 rpm has not much to do with the 
charging.  

An alternate (!) explanation could have something to do with high base load 
(likes LOTS of accessories) dragging the voltage down during idle, or 
pulleys too small to keep the resting voltage up.


bowmanr%em@mhs.elan.af.mil
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