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Q: I have to have the car jumped constantly

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I have to have my car jumped every time I start it. How would a woman knew if it was the battery or the alternator??

My car has 124000 miles.
My car has an automatic transmission.

A: Hi there. Check the battery cables to see i...

Hi there. Check the battery cables to see if they are tight and have no corrosion. Check the voltage with a digital voltage meter on the battery. The battery should read 12.6 volts full charge 100%, 12.4 volts 75% charged, 12.2 volts 50% charged, and 12.0 volts 25% charged.

Only a battery with 75% can be charged. If the voltage is good. Start the vehicle up and let it run for a couple minutes. Check the voltage on the battery again. The voltage should read between 13.5 volts to 14.7 volts.

This voltage is the alternator voltage output. If the voltage is the same as with the engine off, then the alternator is not working. You can apply a load to the alternator with head lights on and watch the lights as you roll up and down all of the windows at the same time.

If the lights are dim, then the alternator is not able to produce enough amperage and this should be replaced. If the alternator is good, then the battery should be replaced. If you need further help pinpointing the problem, a certified technician from YourMechanic can come to your car's location to inspect the hard start and follow through with repairs.

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