What the sheep shit?

[mamzak]

What would cause a battery to be completely drained within a matter of 10 minutes as the engine is running....aside from a bad battery?

[Holland]

Bad Alternator?

[E30Nova]

How do you know the battery was completely drained? If everything was working right, the engine would be running off the alternator, so if the engine just died after 10 minutes, I'd look at replacing the alternator.

Matt

[mamzak]

The engine didn't just die though that's the thing.. I had it running fine and it sounded good but then I shut it off to double check the oil and it wouldn't start back up.

EDIT: When I started it the first time it cranked and fired up nicely so it's not the starter

[lonestar22]

sounds like the alternator is not charging the battery. and the first time there was just enough juice.

either that or the voltage regulator is shot. or maybe an alternator wire came loose

[bimmerpirate]

alternator or a bad cell in the battery.

[mamzak]

sounds like the alternator is not charging the battery. and the first time there was just enough juice.

either that or the voltage regulator is shot. or maybe an alternator wire came loose

I'm hoping it's the alternator because I already have a new one ordered.


A fried voltage regulator woudn't kill the battery though would it? It was a good battery I took out of my Winter Beater (Optima Red Top) so I know it's not a bad cell. I tried the battery in the accord after and it wouldn't start up either so it definitely drained it.


So. 90% sure on alternator?

[jlevie]

My guess is that the battery wasn't fully charged when you put it in the car. That in conjunction with a non-functioning alternator would have drained the battery enough to prevent the car from starting the second time.

Before replacing the alternator make sure that the alternator warning light in the cluster comes on when the key is switched on. That bulb is a critical part of the charging circuit for most E30's* and supplies exciter current to the alternator. If the bulb is burned out, the alternator won't charge.

A shorted regulator will drain the battery in short order. A bit of work with a DMM will pretty quickly reveal whether the alternator is working or if the regulator is shorted.

* Very late production clusters include a bypass resistor to allow the alternator to work when the bulb is out.

[AndrewBird]

I'd check the engine ground strap. Might be loose.

[Burnera]

optima has also gone down in qualiy a lot in the past 8 years or so.

[mamzak]

My guess is that the battery wasn't fully charged when you put it in the car. That in conjunction with a non-functioning alternator would have drained the battery enough to prevent the car from starting the second time.

Before replacing the alternator make sure that the alternator warning light in the cluster comes on when the key is switched on. That bulb is a critical part of the charging circuit for most E30's* and supplies exciter current to the alternator. If the bulb is burned out, the alternator won't charge.

A shorted regulator will drain the battery in short order. A bit of work with a DMM will pretty quickly reveal whether the alternator is working or if the regulator is shorted.

* Very late production clusters include a bypass resistor to allow the alternator to work when the bulb is out.

I think my date of manuacture is August of 1990... would this have a bypass resistor then?

[jlevie]

It might. If the bulb works, it is a moot point. If it doesn't a check at the exciter terminal with the ignition on will tell if exciter power is present.

[mamzak]

groovy! Thanks man!

[Simon S]

That 'Bond' sig is friggin sweet !

[txtorquemade]

that 'bond' sig is friggin sweet !

+1