Remove cover and filter and using a sprayer bottle with a water and mild soap mix spray the coils dont wipe them you will damage unit plus probably get injured spray really well let sit for a few minutes than turn on fan and start spraying again the fan will draw the solution throught the coil and the solution will also clean down condensation pan and then drain out back --other problem would be a bird or critter took up living by the condenser and you will need to remove the frame cover to access that area