Car problems--won't start, help?

[Ego]

Hum. I've bump started plenty of cars (maybe 20) in my lifetime with dead batteries and they all started fine. Well, except for that time when we had just finished hiking the Grand Canyon and I had to push the van while Mrs. Ego popped the clutch, started the engine, then stalled it..... a half dozen times..... Man, just thinking about that pisses me off. See what you did!

[JL13]

Ha sorry to bring up bad memories! There's dead and there's really dead. A 'dead' battery may have 12v and be able to put out a few amps - that's enough for the computer but not enough to crank. That's a situation a push start is fine for.Most batteries that are "dead" are really just say 50% charged so they're like 12.1volts. Fine for push starting.

What I'm describing is a dead, i mean really dead battery which is below 5v and less than 1amp. that's not enough to power the computer on. and a push start will do nothing. If you've got enough juice that you see dash lights (oil, brake, check engine etc) then you're ok to push start. If you see nothing at all - you can't push start it.

In college I had a battery that couldn't put out enough juice when it was freezing outside to crank the engine. I always parked on a hill on cold nights and popped the clutch in the morning.

[Sclass]

So no battery power = no electromagnet = no power generation by alternator.

True in the majority of cars. There are self exciting alternators out there...I built a custom car with one once...it was out of a GM car. Motorcycles often use permanent magnet rotors in their alternators.

Come to think of it, the dash lights glowing means battery power is flowing from the battery to the "electromagnet". This is why the ALT light glows when you aren't charging...I think. Once your car starts regulating above the battery voltage, the current switches direction and the light doesn't come on because of a diode...I think. I'm rusty on this stuff.

[Dragline]

You know, we[re beginning to sound like the "King of the Hill" guys out standing by the road in front of their suburban houses drinking beer.

Then again, maybe that's not so bad in principle.

[Peanut]

Yippee! Car is working again. New battery did the trick. I even helped install. Didn't see much corrosion, but my friend says if this one dies quickly I have an alternator problem, so fingers crossed.

Now what is the over/under on Peanut driving a manual tranny 2008 VW? I put it at 50-1 against.

Haha, and those are good odds! I've barely sat in a manual transmission car, let alone tried to drive one.
@Ego: Definitely reside in the good 'ole.

Thanks again for all the troubleshooting!

[Ego]

Crap. 0 for three. You ruined my day.

Glad you got it going.

[JL13]

HA Dragline. C'mon we're supposed to be polymaths right?

@Sclass - IIRC I think the charging light is normally grounded via the diode bridge in the alternator. When the alternator is charging though, the "ground" is alternator charging output of 12v. Therefore 12v on both sides of light = no ground = no light.

[Sclass]

HA Dragline. C'mon we're supposed to be polymaths right?

@Sclass - IIRC I think the charging light is normally grounded via the diode bridge in the alternator. When the alternator is charging though, the "ground" is alternator charging output of 12v. Therefore 12v on both sides of light = no ground = no light.

Ahh yeah that's it.