Performed preventative maintenance for a Lennox system. Checked drain pan and drain line for any possible clogs. Checked the evaporator and condenser coils for buildup. Checked all electrical components needed for air conditioning. Removed the screws from the filter slide and covered it with aluminum tape. Filter slide is wedged between fixed return duct and fixed furnace. Replaced air filter (16x25x1) The system is operating properly at this time and is ready for the summer season. No Charge FWI