My battery died. Got a jump, but my car wouldn’t stay running for more than a few seconds. I thought once you got a jump, and the car was started, you were OK (as long as you didn’t turn off the engine). Does this mean the alternator isn’t working?
If you jumped the dead battery, and then removed the jumper cables and let the alternator try to recharge the dead battery, you can fry the alternator.
Tester
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jumper car is working ok. U hook up jumper cables to dead battery. Jumper car is still running. You start dead car. Dead car alt is working now. Jumper car alternator is also still working.dead battery wants full amps. It has 2 alternators feeding it now.
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Yes, I bet the alternator isn’t working, and maybe the battery is too far gone.
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If the battery has failed and has no internal resistance the charging system voltage will be unstable, the engine may stall. Don’t assume there is a charging system failure, battery failures are more common. Have the battery and the charging system tested.
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Try leaving the jumper cables on the battery for a few minutes before you jump the vehicle. If it dies after that then you may need a new battery and alternator as well. Replace the battery and check the charging voltage to make sure your alternator is ok.
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I would put that battery on a charger for the night and then try it. If you have no charger, most auto supply stores will charge a battery for you.
Then if it starts and keeps running , you can test the voltage to see if it is charging.
You will need a DVM to test the voltage.
You should have 12- 12.5 volts not running and 14- 14.5 volts with the engine running at the battery.
Do not remove a battery cable while the engine runs to test the charging system.
That only worked on the old cars and can damage the charging system on cars made after the 1960s or so.
If you get the same voltage on the battery running and not, then you can test the alternator.
DVM negative lead on any clean metal ground and touch the positive lead to the post on the back of the alternator (engine running).
Use care that you do not touch that post with the probe and the alternator case at the same time.
If that post reads 14 volts but at the battery you only get 12 volts (engine running) then it could be the wire that runs from that alternator post
to the battery. This wire carries the charge to the battery, and is a fusible link…meaning that it acts like a fuse and once burned out, the link (wire) must be replaced.
Yosemite
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You should get a dash light indication if the alternator is not working…The battery and charging system need to be checked…First step is to be sure the battery terminals are CLEAN…
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Thanks for all the responses!!!