I have an old AC unit that is leaking. The old condenser drip pan is plastic and was put ontop of the furnace without a gap or metal to protect it. The heat from the furnace melted a hole in the drip pan and my basement floor is wet. AC guy said he can't just replace the pan, but has to change the whole coil and everything. Initial service call, new flame sensor, replacing coil and drip pan, going to cost me $800.00. The AC works great, so why do I have to have the whole coil replaced. Seems like a metal cookie sheet would work to replace the plastic pan!?