Spring tuneup cleaned coils, brushed and cleaned traps, added pan treatment tablets to pan. tested and checked all controls, wiring connections. tested temperatures, checked filters. checked refrigerant temperature and pressures, tested static duct pressure. tested blower operation, tested cooling operation to ensure working within manufacturer specifications. I moved all the combustible stuff that you had on top of your gas water heater. Nothing flammable should be put on top of that as that’s the open exhaust pipe pulling in secondary air this will prevent a fire by keeping combustible stuff off the top of the gas water heater.