I have a 2003 toyota camry xle, recently the car has died after the battery light came on. the battery read 12.5 volts and after jumping the car and removing the battery it died suggesting the alternator was bad. The alternator was tested bad and thus bought a new one and installed.

after the installation the car would shut down if idle after being jumped. it would run fine if a small amount of gas was applied. after 20 min with the car connected to the jumper cables the car would then idle fine. I even removed the battery while running to make sure the alternator was in fact working. the strange thing is that when the battery is hooked up it reads 12.5 volts idle, i was told it should be around 14 volts.

after running for around 30 min i took it out and the car ran fine then when i returned and shut the car off it would not start again. battery still read 12.5 volts.

in February of this year I had replaced the battery cables however they look fine now i plan to double check them when i get off of work.

I was wondering if there should be any other item to test/ check?

and as always thanks for your help.

  • 2
    Welcome to Motor Vehicle Maintenance & Repair! For future reference it is a really bad idea to remove the battery from the charging circuit while the engine is running. It's a really good way to fry your alternator. This used to be an old school method, but now is very poor practice and really doesn't tell you anything. Not only can it fry your alternator, it can also fry electronics inside the car. The battery acts as a load buffer, which can tame voltage spikes. Without it ... zap goes the weasel. Dec 20, 2018 at 17:07

1 Answer 1


With the engine off, voltage at the battery should be 12.5 volts.
With the engine running, voltage at the battery should around 13.8-14.5 volts.
I recommend using a multimeter to test this, not disconnecting the battery.

If your alternator is not supplying 14v with the engine running, I would have it tested to make sure it is functioning properly. If the alternator is functioning properly, I would look into the wiring. Test the voltage at the large wire coming out of the alternator. This should be the same as the battery voltage. There is a connector with 2 or more wires. Make sure this connector is firmly seated in the alternator. Follow the wires back to be sure they are not damaged.

Another possibility is a bad ground. With the vehicle off, test the voltage between the alternator case and the positive side of the battery. It should be the same as the battery voltage. If not, check your ground wires between the battery and the body or engine.

For more specific testing of the alternator circuit, you will need a repair manual with schematics and / or troubleshooting steps. This typically involves testing the wires on the connector.

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .