You should buy COIL CLEANER from any heating and cooling supply house. Remove the cover if possible and spray the cleaner on then rinse with water.
If you have a weed sprayer that will work for the water as you do not want to flood the evaporator coils inside and make a mess.
Force of air or water is not recommended. Try and apply everything straight on to the coils as this will get the cleaner in farther.
WBCCI 12156 AIR 3144 WACHUNG TAC NJ6
2004 Excursion 4x4
1991 34 ft. Excella +220,000 miles, new laminated flooring, new upholstery, new 3200 lbs axles