Is your ignition warning light working correctly? The light is necessary to
supply the initial excitation to the field of the alternator which starts it
charging. However on a used alternator you may well find that charging will
start anyway but not until 3000 rpm or so.
The ignition warning light should glow when you first turn on the ignition.
Once the engine starts the light should go out the first time the revs go
over 1000 rpm or so. Then when you switch the ignition off the light should
glow again until the engine stops spinning (this may not happen on cars with
an ignition relay).
Check that you have 12v on the thick brown(s) with the ignition both on and
off at the alternator plug. Check that you have 12v on the brown/yellow at
the alternator plug with the plug off and the ignition on.
If all that is OK, with the engine running, measure the voltage at the thick
brown at the alternator plug. If it is still 12v then logic still says that
the alternator is bad. Did the parts shop test it on load?
PaulH.
-----Original Message-----
From: Steven Miller <bonding@hotmail.com>
To: mgs@autox.team.net <mgs@autox.team.net>
Cc: smille@earthlink.net <smille@earthlink.net>
Date: 10 November 1999 23:12
Subject: charging problems #2
> After taking out the alternator, and bringiing it to a parts shop to
test
>it, it checks out fine. They get a voltage comeing off of it at 14 volts.
>So I can only think that it is one of two things. The pully assembly and
>original alternator was the wrong one for the car. The pully when fit on
the
>new alternator is too big. I know that I should get the right parts, and I
>will probably order them tonight, but I am kinda on the broke side. Having
>said all of this here is the current situation. The belt is tight, and the
>pully is as centered as I can get it, the car runs fine and does not throw
>the belt. That is the good new. The bad news is that mounted in the car
>(with the three prong connecter plugged in) I am getting not getting enough
>voltage from the alternator to charge the battery. In fact with all of the
>lights off, I slowly drop in voltage until I reach ten volts, then it
levels
>off and I do not get any change until I turn lights on, then the voltage
>starts to drop.
> Finally, I guess the question is this... If I disconnect the three
>prong connector and hard wire the alternator to the battery, am I going to
>have a problem? Can I disconnect the connector on this car and start the
>car, or will that fry the diodes in the alternator? I am truly at a loss,
>is it possible that something in my car is causing such a drain that the
>alternator cannot keep up?
> I am at this point desperate, I need a car to last me one more month,
>the MG was supposed to be my fun car, you know the one that if it broke
down
>was supposed to be no big deal bucause I could fix it at my leisure...Sigh.
>In one month I am getting a 94 buick century, not a fun car but one with
>only 14,000 miles on it. I just need this car to last (the MG) until dec
>10.
> My other car is so close to dead I am not even going to give the honor
>of mentioning it in this letter.
>Please if anyone has any thoughts, please write to the list or:
>
>Smille@earthlink.net
> or
>Bonding@hotmail.com
>
>Thankyou all for all of your help!
>
>Steve Miller
>
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