jeep battery drains only sometimes
My moms Jeep grand Cherokee I think 2004 has a drain on the battery. I go up to her house once a week to take her grocery shopping. she drives it to get her mail a couple times a week. Sometimes its fine but other times its completely drained no lights ect but I hear a motor running its very faint from under the dash. I plug battery charger in and it stops. When I unplug it the motor continues. I have noticed this noise each time the car doesn't start but cant figure out what it is?