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Need help quick (electrical problem)
derf - 5/10/05 at 02:46 PM

I tried to start my car and it was dead. Then I tried to jump it, it would start and then immediately die as soon as it was dissconected from the other car.

I know the battery is dead, I plan to grab another battery from my house as soon as I can, but I am sure that if the battery is dead and the car is started the alt should be putting out enough juice to run the car. So I'm thinking that the alternator is dead.

Am I right?

theconrodkid - 5/10/05 at 02:51 PM

if the battery is dead as oposed to flat then it prob wont run,alternator need some voltage to "switch on" the magnetic feild in the windings

BKLOCO - 5/10/05 at 02:54 PM

Yes.
Once started you should be able to remove the battery completely and engine will still run

flak monkey - 5/10/05 at 03:18 PM

BKLOCO, thats not quite true....

On a modern car with EFI etc you need the battery to run the car and all its electronics. Sad but true fact. Old cars you could disconnect the battery.

Point in case was my sisters car. Battery died, but jump started it, was ok until you put the headlights on and it pulled all the power from the battery and the car would stop.

David

theconrodkid - 5/10/05 at 03:41 PM

disconecting the battery with engine running wil fooooooobar the alternator in seconds

britishtrident - 5/10/05 at 04:26 PM

quote:
Originally posted by theconrodkid
disconecting the battery with engine running wil fooooooobar the alternator in seconds


100% Right you were also 100% correct in your earlier post ANY alternator will not charge a flat battery ie one with less than about 8 volts no load voltage.

britishtrident - 5/10/05 at 04:28 PM

quote:
Originally posted by BKLOCO
Yes.
Once started you should be able to remove the battery completely and engine will still run


No -- unless it has a dynamo rather than an alternator.

britishtrident - 5/10/05 at 04:33 PM

quote:
Originally posted by derf
I tried to start my car and it was dead. Then I tried to jump it, it would start and then immediately die as soon as it was dissconected from the other car.

I know the battery is dead, I plan to grab another battery from my house as soon as I can, but I am sure that if the battery is dead and the car is started the alt should be putting out enough juice to run the car. So I'm thinking that the alternator is dead.

Am I right?


Check the battery terminals are making a good clean tight connection - then Put the jump leads on and leave it with the other car running at a fast idle for about 20-30 minutes -- this should be enough to give an initial charge BUT it only works with oldfashioned lead acid batteries it won't work with the latest types of batteries.

[Edited on 5/10/05 by britishtrident]