let it idle for 20
shut it off
tried to start and its dead again.
Battery or Alternator?
Lets test both the battery and alternator before spending money on parts you do not need:
#1.Take the 12 volt battery to any store that sells new ones *other than Auto Zone. Ask for a free 15 second battery load test to see what the reserve amperage capacity is. Amperage spind starter motors not voltage.
#2. When a new or fully charged battery has been installed, touch the battery terminals with an inexpensive volt meter *set @ 20 volts with the engine running. IF the alternator is charging properly the volt meter will read between 13.5 - 14.2 volts.
#3. Stay away from Auto Zone. They have no clue what a battery load tester is!
It is hard telling. If it ran for 20 minutes and is a recent model car, if the alternator was bad, the battery would not have been able to provide enough electricity to run the fuel injection system for 20 minutes. I would guess battery. You could jump start the vehicle again and use a volt meter to measure the voltage at the battery while the vehicle is running. If it is over about 12.5 V, your alternator is working.
Can't tell from what you have said. Could be either.
You need a meter and measure the voltage across the battery with the engine running.
If it's only 12V, then the alternator / regulator is faulty and not charging the battery.
If it's about 13.8 V, then the alternator / charging circuit is working, so it's a dead battery that's not holding charge.
Ah, you can't charge a dead battery with a dead battery. An alternator uses and ELECTRO magnet to produce power. In other words, if the battery is dead, there's no electro magnet. Read this post on the correct way to charge a battery. Plus, you can't test an alternator on the vehicle when the battery is dead
http://ricksfreeautorepairadvice.com/cha...
It sounds like your alternator is draining all the power. So you will need to replace that. But I would replace both just to be safe. That's if your battery is old if its fairly new I would recharge it and get put in a new alternator
well it could be both but if the battery is more then 5 years old it's most likely the battery
If you live close to autozone they will and can test each for free and let you know exactly what is wrong with it.(my guess is 50/50 alt.)
jumped car with another car
let it idle for 20
shut it off
tried to start and its dead again.
Battery or Alternator?
