Never disconnect the battery when car is running. I know that used to be the old way to check if alternator was working, but that was before electronics became the norm on vehicles. On today's vehicles, or any with a computer in it, disconnecting the battery with key on, or engine running, there is too great a chance you could fry the delicate electronic circuits that the computer requires. Always turn key off before disconnecting the battery.
Okay, enough soap-boxing. You need a new alternator, if the car won't run with battery disconnected. Next time, use a volt meter.
SOURCE: Car won't stay running.
alternator does not hold a charge it simply charges the battery by unhooking the battery you are taking all voltage from computer and car will not run the proper way to test your alternator is use a multimeter and check voltage at battery while car is running if you have 13-14 volts it should be fine.
SOURCE: Volvo 240 wont hold charge
if with the volt meter the amps go down while running and at increased rpms than your alternator is not charging right
SOURCE: Battery wont charge in my 1997 ford crown victoria
In the 1995 and later Crown Victoria's, there is a fuse in the fuseblock that controls the alternator's charging of the battery. If that fuse is blown, your car will drain the battery and cut off as you stated.
Check the fuse block under the hood and the one located on the left driver side above the hood pull.
SOURCE: 98 cadillac deville battery wont hold a charge
sounds like a 12V drain on the system, like a trunk or glove box light that won't shut off.> Could be many. many other reasons why. The way I would find the draining circuit would be to remove the neg cable of the battery. I then would connect a 12V test light between the neg battery TERMINAL and the neg battery CABLE. With a 12V drain the light will shine. I would install into the light a 9V battery powered recepticle to hold computer and radio station memory. Then I remove fuses 1 at a time, then reinstall, at the same time looking for the 12V light to go out. Hope this helps.
SOURCE: Battery in 1994 olds ciera will not hold a charge
Take a voltmeter with the car off and measure the voltage, should be around 12V. With the car running, measure again and this time it should read 13V-14V. If it does read 13V-14V then it means that the alternator is working. If it is below 12V, then it means your alternator is not charging the battery. If it's above 14V, then it means your alternator is overcharging and damaging the battery.
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