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Originally Posted by aarong420
the battery reads aprox 12V when the car is off. It still cannot start, probly cuz it has no amp pwr to turn the engine. If i start the car with another battery, it runs. but will die when i put on the lights, or any other electrical component.
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The battery voltage when you don't have a load on it frequently doesn't tell you much. The battery might not be capable of holding much of a charge but could still read 12V when not under a load. Leave the multimeter connected when you try to start the car. If the voltage drops below about 8 V then the battery doesn't have enough of a charge. But if the battery voltage stays high (near 12V) and the starter motor still doesn't crank the engine then you should check for loose or corroded cable connections on the battery clamps, starter motor, or the ignition switch wiring.
As toyota_b said, check the voltage when the car is running so you can see if the alternator is charging the battery. The multimeter should show about 14 V when connected to the battery while the engine is running.