Why would a car air condition freeze?
Low air flow. If you have a low air flow as produced by the fan
blowing the air cooled air inside, then the coils will have a
tendency to freeze. The explanation is that the air flow, warms the
refrigerant up as it cools the air in the process. If the air flow
is low, the refrigerant does not heat up as much, so that when it
loops back to pass through the expansion valve, it is starting off
cooler than before and thus becomes colder with each pass, until
the coils freeze up on the inside and the AC fails to work
properly. Low refrigerant. The second issue of the refrigerant
being low in the unit is based on the above principle as well.
Remember that when the freon passes through the expansion valve it
expands and thus cools. Well, if there is less refrigerant in the
coils as it passes through the expansion valve, then the
refrigerant is allowed to expand even more than before because it
has more room. Since it can now expand even more, it will thus cool
that much more. As the refrigerant level drops, this expansion
increases more and more, until this chilling process begins to
freeze up the coils on the inside and the unit fails. So have your
unit checked by a professional. You more than likely have a leak
and it needs to be repaired before adding more refrigerant.