A/C swittch must be turned off then on to keep air cold on 1992 Subaru Loyale

I have a 1992 Subaru Loyale, great running car, but with an issue that is puzzling me. My A/C works ice cold, but then after a while the air starts to get warm at which point I have to turn it off then back on, which then starts the cold air flowing again. It is very consistent in doing this, but I am afraid the turning on and off to maintain coolness will eventually hurt something. Can anyone give me some insight as to what is causing this?
Thanks!

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1 answer 1 comment
The evaporator coil is freezing up due to hot ambient air temperature and by turning it off gives it a little time to defrost. Try running the A/C in RECIRC mode instead of FRESH mode. This will help with frosting up
Thanks so much... I will give it a shot... wish me luck!.. Thanks again..much appreciated!