if a car will only run after a jump start, is the problem with the battery, or the alternator?

Answer 1

If you jump start the car and it runs OK until you shut it off, then the trouble is the battery. If the trouble was the alternator, the car would not run long after a jump before it shut off. Well, depending on the time of day and how much electricity it needed. Things like radio, windshield wipers, lights, or heater all need electricity to work. The battery would not supply them for very long without the alternator.

Answer 2

If the car will only start after the jump start (battery to battery connection) it implies that there is not enought stored energy remaining in the battery to provide sufficent amperage to turn over the starter motor and provide the spark to get the engine to run.

----You'll often find that alternatively with the same battery you can Jump/bump start the car (ie roll it in gear get enough speed let clutch out) and it will run....this being the case because the momentum of the car moving does the job of the starter motor which the battery doesnt have the energy to do, but the battery still has enough to provide the spark to casue the ignition.

Once an engine is running..if your alternator is not working, it will not be able to provide enough charge to replenish the stored energy in the battery so the car would - if a new battery fitted for example die very quickly becasue the energy being used by the car to run would not be topped up by the alternator.

Ie - battery provides power to car whe engine is not running (to start)
- Alternator provides energy to car when running and charges up battery.
-If alternator broken no charge to battery, no start and fully charged battery only works for small amount of time
-if battery only problem jump start will get car going and car will continue to run (but if cells in battery broken then even the working alternator cant charge it as cells wont hold power - casuing it to need jump start every time)

Answer 3

First, see if the Battery will take a Charge, if it Charges around to 3/4 on the Meter after about 8/12 Hours it should be ok.

The Alternator Charges the Battery after about 8 Miles if its Faulty
then it will Drain any Power from the Battery

You can always get them Tested at a Garage after you have given some Life to the Battery to find out for Sure.

Answer 4

If you turn on the headlights, are they BRIGHT? If so, the battery is fine.
Get a multi-meter and read the voltage your battery is putting out across the terminals without the motor running. It should be approximately 12.5-13V.
When the motor IS running, you should be able to read voltage from somwhere between 13.5-15V with the alternator WORKING. If you get 12.5 V across the battery when the motor is RUNNING, your alternator is not working.

If the voltage is 13-15V when the motor is running, the battery and alternator are probably both okay.

If the car jump starts just fine, the battery is likely the problem HOWEVER, since a vehicle CAN run, once started, without the battery, IF the alternator is WORKING, get it?

Take off the battery cables, clean the posts and terminals and reinstall them. If the voltage was 12V + the car should start.

Answer 5

it particularly relies upon on how previous Your battery is, is there any electric problems that must be draining your battery. From what you have suggested, i'm particular its the battery simply by fact if it particularly is the alternator, each thing would be ineffective. I propose no lights interior the tool panel, no chimes once you turn Your key. yet just to verify, have a mechanic do a battery examine on an identical time as the engine is working. The try would be sure additionally in the adventure that your alternator is producing adequate voltage to ability the entire automobile's electric needs.

Answer 6

Most likely it's the battery. Another strong possiblity is excessive corrosion on the battery terminals.

You can clean corrosion off yourself pretty easily. Disconnect the battery, negative cable first. Clean the terminals with a wire brush or a battery terminal brush. Rinse the terminals and the battery case with a solution of 1 or 2 tablespoons of baking soda in a quart of warm water. Be careful that you don't get any inside the battey, though; make sure that caps are on tight! Rinse off with plain water and dry with paper towels. Hook everything back up and see if the battery will hold a charge now. If it won't, its time for a new one.

Most auto parts stores and tire and auto centers (Sears, Wal-Mart, etc.) will run a quick battery and charging system test for free or a very low cost.

Answer 7

Most of the time, especially this time of the year, it will be your battery. If your current battery is 3 years or older, you may require a new battery.
Remember to check your alternator belt to make sure it is properly tight enough to recharge the bettery. Have the alternator checked at a local mechanic before you replace the alternator.

Answer 8

If the Battery light goes out on the dashboard with the engine running the alternators charging if not then the alternator is faulty

Answer 9

It could be one or the other. you need a multi meter to test if the alternator is charging the battery.with the car running put the meter on the the battery (+ & -) connections you should get a reading of 14.5 volts or above and if you rev the engine a bit the reading will go up. then its your battery or take the car to your local garage they should do the test for you.

Answer 10

I would think it would be the battery. I had a bad alternator and my car did not run for long.