I recently had to replace the alternator on my 01 2.2 and since doing it, the car is having a problem with a dead battery in the morning. Tonight, I hooked up a battery charger and discovered a hum under the driver's seat. What is it, could it be draining my battery and can I just unplug it?

 

Does the car have electric powered seats, heated seats, aftermarket stereo amp, alarm system, remote door locks or starter?

The internet has video's for tracking down parasitic drain. Basically using an amp meter to check current draw at battery and pulling fuses until it goes away. There is always some current draw around 50ma.