In the summer my air cond wouldn't operater; jumped low pressure switch which engaged the unit to work, so had tech recharge freon and repair 2 outside valves. Now heat not working; fan on but not igniting. The furnace exhaust pipe was actually rusted where there are at leat 5 visible holes, so obvious moisture (tore the piping out). Could this all be a result of improper drainage from the furnace? FYI I have a carrier heat pump connected to the air cond and furnace.