Why won't my battery turn over when using accessory power? on 2003 Saab 9-3

If I sit in the car and listen to the radio even for 5 minutes or have the keys in the ignition and door open when loading the car, the battery drains completely and I need to get a jump start. All other times the car starts with no problem. Also, there's a constant humming like something not turning off coming from the cigarette lighter and it's never used. Thanks!

Asked by for the 2003 Saab 9-3
2 answers
You have a bad battery. Have it tested.
Your battery is too old. Test the voltage while you're cranking it and you'll find it less than 10.5 volts which isn't enough juice to start the car.