Dan O. -- Friday, 7 June 2002, at 1:43 p.m.
: I have a 24000 btu window unit which is
: freezing up with frost on the coils after
: running for 5 or 6 hours. I am cooling about
: 1000 sq. ft. I did not have this trouble
: last season.
If the evaporator (cooling) coils are frosting totally, the most common cause is that the indoor or outdoor air temperature is colder than will let the air conditioner to run properly. Both inside AND outside temperature must be above 70°F in order for the unit cool properly and avoid frosting up.
Another cause of the evaporator frosting totally is poor air flow. Make sure the front grill is on the unit with the louvers set properly and there are no obstructions in front of the air outlet like curtains or furniture and that the filter is clean.
If the evaporator coil is only partially frosting, the most common causes are a plugged or partially plugged condenser or the unit being short of refrigerant. The latter case is fairly rare in a window/wall type air conditioner unless damage has been done to it.
Such a unit should be professionally cleaned at least every 3 years or every year if used in a high traffic area.
Dan O.
