Have a 1992 240 four door that runs great. Recently I have been driving my other car (76 245) almost every day and letting the four door sit. After it sat for about a week, I hopped in to start it and dead battery. Put the charger on, it started, drove it all day. Week later, go to start again-dead. Put the jumper on and as I did, heard something running under the hood, disconnect charger, noise stops. What would be running off the battery when the car is sitting with the key off and killing it? No lights on, no key on, nothing. Something is obviously using juice when it shouldn't. any ideas?