Re: Charging delays in 4000

[Robert F Phillips <r3rfp@dax.cc.uakron.edu>]

On Fri, 20 Jan 1995, Alan Cordeiro wrote:

> >Amidst the rest of the charging questions, here's another:
> >87 4000S, 4-cyl, at start up, the alternator does not charge at all until 
> >the revs rise to around 4000.  After the alternator "kicks in", it 
> >charges perfectly until the car is shut off again.  Then the cycle 
> 
> However, most manufacturers provide a method of supplying the
> field winding  with about 0.1 amps, ( don't need much ) to
> help it come right up at only 800 to 1000 rpm. They feed the
> battery positive to the "charging lamp" when the ignition
> is switched on, and the other side of the lamp goes to
> ground THROUGH THE FIELD WINDING. Once the field supply cranks
> up, the lamp goes off, since there is 14 volts on both sides
> of it.
> 
> Possible causes of the effect you are seeing
> 
> 1)  Burnt out indicator lamp.

Well, you certainly seem to know what you are doing.  I think I might 
have either left the socket empty for the bulb in question or it may be 
burned out.  You see, in my efforts to repair my dead odometer, I may 
have left the charging light disconnected or just removed the bulb to 
save the confusion of reattaching it.  Bob thinks, "Heck, we don't need 
them durned things any way!  We gots a volt meter.  Idiot lights, huh?"  
I think you may be onto something.
So, if the circuit is open (broken/off) the alternator would indeed not 
begin to charge until enough rpms are built up at the alternator, right?  
If the "pre-charge" circuit does go through the indicator lamp, that's 
probably what's happening.  I note that once the alternator "kicks in",  
it charges excellent and I have had no battery problems.  If the 
"pre-charge" circuit is indeed broken, would the alternator charge fine 
once the given rpm of the rotor is reached?

Stupid question: what type of icon does Audi use for the low battery 
and/or alternator warning light?  I know the check engine light shines 
when I turn on the key, the low-oil-pressure buzzer screams, but I am not 
sure which one is for the battery/alternator.  I probably shouldn't have 
unplugged all of the indicators at once without noting where the little 
suckers go... :(  Time to visit Mr. Bentley..

P.S.  If the circuit is good, would leaving the key in the "on" position 
longer before starting the engine help to pre-charge the alternator?  
Just a thought.  But, if the circuit is bad, it wouldn't do anyhting, right?

			--Not an electrical wizard,
				--Bob