Alternator problem and... ?

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Ludwig - 29 Dec 2005 01:31 GMT

Recently I replaced the worn-down brushes in the voltage regulator. My
battery having been depleted, I got a jump start and the engine ran,
but the charge light was still illuminated, and as soon as the jumper
cables were removed the engine died. Now I've fully charged the
battery but it won't start at all, and the charge light is very dim
while the starter chugs. Obviously there's still a problem with the
alternator, but shouldn't I be able to start and run for a while just
off the battery, as it did off the jumpstart donor?

Thanks,
Ludwig
1990 C900T

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Craig's Saab C900 Site - 30 Dec 2005 05:10 GMT

>Recently I replaced the worn-down brushes in the voltage regulator. My
>battery having been depleted, I got a jump start and the engine ran,
[quoted text clipped - 4 lines]
>alternator, but shouldn't I be able to start and run for a while just
>off the battery, as it did off the jumpstart donor?

First of all check all the wiring connections to the alternator,
particularly the ground connection.

It might not also hurt to reach behind the instrument cluster (I'm thinking
of C900's here) and push the two multi-pole connectors into the back of the
cluster properly just in case they're loose. That's to see if the
connections to the charging lamp are not good since if the lamp blows or
becomes disconnected due to wiring elsewhere coming astray, the battery
won't charge at all.

If you would like to give the alternator a thorough test there are a few
ways - most of us (me included) don't have proper alternator testing gear so
have a look at these URL's to get some ideas:

http://www.swedishwrench.com/battery.htm

http://townsendimports.com/Web/electrical_system_folder/altbushregreplace.htm

There are no doubt other good references covering alternator and charging
system 'debugging'. If anyone knows of more, let us know.

Regards,

Craig.

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Ludwig - 30 Dec 2005 08:56 GMT

But why would it start off of a portable jumpstart thinger and not its
own battery which reads 12.55V with the key off? That's what mystifies
me.

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John B - 30 Dec 2005 17:38 GMT

> But why would it start off of a portable jumpstart thinger and not its
> own battery which reads 12.55V with the key off? That's what mystifies
> me.

Probably the battery has good voltage but cannot produce suffcient current.
I think this is common.

John

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darthpup - 30 Dec 2005 17:49 GMT

If you have a new battery in the car it will read 13.8 volts when fully
charged. Replacing the voltage regulator without cleaning the
armature, which builds up oxide and carbon over time, may not cure the
charging problem. Like the other poster suggested you most likely have
poor connections from the plus and minus side of the battery. Try
cleaing the ground to frame connection carefully.

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Misterbeets - 02 Jan 2006 16:46 GMT

Alternator may be grounding the battery positive terminal. I would undo
all connections to it and start over.

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