help leaking water

water is leaking inside of my car underneath the glove compartment, the black box under there. some people i know tell me it is my heater core but the thing only drips water when the AC is on. if i am correct the box would leak once the car is running not just when the AC is on. thething i think it is, is a hose that got disconnected somehow. if anybody has any help please tell me what the problem is and if they know how much this should cost to fix.

take it 2 the shop

If the heater core is bad, its gonna leak anti-freeze.

The water is coming from the evaporator

That happened to me. Check the water pump.