Furnace and air conditioning maintenance While inspecting the furnace, notice water at the bottom of the furnace and noticed a lot of water stains. Cut a hole in the supply plenum at the back of the furnace and noticed the air conditioning evaporator coil is leaking water onto the furnace. Back right hand side of the drain pan appears to have a small crack in it and the physical coil itself is rusting. Water leaking onto the furnace can cause damage to the furnace heat exchanger. The heat exchanger appears to have over heated at times and is turning purple / black. There are small stress cracks through out the heat exchanger. Heat exchanger is still in safe working order, but highly recommend getting a furnace inspection / maintenance yearly to ensure it’s still safe due to the condition it’s currently in. Due to the condition of the air conditioning evaporator coil, customer agreed to not do air conditioning maintenance, and would like to explore evaporator coil repalcement Vs