2001 Ford Mustang mileage: 69,000. My son's car failed to start after school on Friday even though it had run fine that morning. We jump-started it thinking he had left something on. We took battery to get charged and they suggested new battery so we bought one and put it in. The car immediately cranked, but after setting overnight without driving the car for more than a few minutes, it was dead again this morning. Nothing has been left on to run the battery down, and I thought it might be the alternator, but since we didn't run it, yesterday I didn't see how it could have pulled all of the juice out of the battery if it was alternator.I feel like something is running the battery down, but don't know where to begin to look. Any ideas?
Here is the procedure we use to isolate a battery drain. Remove negative battery cable from the battery. Using a 12-volt test light, hook one end to the negative battery post the other end to the negative battery cable you just disconnected. The test light will glow or light if there is a drain. If the light or glow is faint, that is probably normal draw for the clock or computer. If the light or glow is bright, then there is a large drain. That should be corrected. Now start removing and replacing the fuses one by one until the light goes out; that one will be the circuit with the drain. Remember to hold in the button in the door jam for the interior lights.
February, 10, 2011 AT 8:53 PM
To add to the previous answer, most vehicles these days have various timers for lighting and other things that trigger every time the power is interrupted so you may have to wait for these to expire to see if you really have a draw or not. It may be more accurate to use an ammeter in place of the test light to get a more accurate reading on the parasitic draw. The acceptable range is under 50ma.