Something's running in the emission section under the hood

What is your question?

I have a 2000 MBZ E320...after I shut her off I hear a whirling sound and then a click that repeats every three or four seconds...the sound is coming from the emissions console under the hood which is right behind the glove box (passenger side), even with the key out of the ignition and the doors locked...it is draining my battery and I can even see the the car battery charger needle jump when the click sound occurs? What the Hell is going on?