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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?

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Wiki User
2007-11-29 23:53:59

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.

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