Why does ac quit blowing cold air after two hours in a 95 Lexus ES300 Park for 30-45 min and starts to blow cold air?

Next time it stops blowing cold air, leave the engine running, AC on, and open the hood. Check the AC lines under the hood. If you see a lot of frost buildup on the AC lines, there's a good chance you also have frost buildup on the evaporator inside the air-handler. It's called "icing-up", and it's generally caused by someone over-charging the refrigerant (over pressure). When you build up too much ice, the air can't blow past.

Correction: My understanding of the AC theory and many actual occurences over 30 years is that the icing happens when the AC charge is low, not over-charged. I know this is counter-intuitive, but, if you research how the evaporator ices up, it has to do with too low a refrigerant pressure, not too high! So, the solution is generally to add refrigerant.

First answer by Ifetterley. Last edit by Ifetterley. Contributor trust: 13 [recommend contributor]. Question popularity: 32 [recommend question]

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