Is my car battery dead and my car is running off the Altenator alone?
If you remove the negative cable with the engine running and the engine continues to run – it is a good backyard test of the alternator. That would mean it is good. Check the battery with a voltmeter. It should be a least 12.0 – 12.6 volts fully charged. If it is not – charge the battery – take a voltage reading – allow to sit a couple hours and read the voltage. It should still be the same – if not the battery is not holding a charge – replace it. hope this helps – www.trucktechautoandrv.com http://techman77.wordpress.com/ Taking the cable off for a brief second to see if the engine dies or not will not fry the computer. I’ve done it a hundred times. I wouldn’t recommend leaving the cable off for any length of time but if the alternator is bad it will start dying immediately then simply set the terminal back on the battery.
Do not remove the cable while running you may damage the computer on the car. Take the battery out and have someone charge it and check it. If you continue to just jump it and drive a dead battery you can fry the alternator. Alternators these days just maintain the battery etc and continuous full charging will kill it.
