Q: air conditioner blows hot and cold air when it is supposed to be just cool air on 2000 BMW 323Ci

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My air conditioner blows hot and cold air. The cooling is very uneven. I have just spent $870. and it is just as bad as it was originally before they "fixed it".
2 valves were replaced, one high pressure and the other one was low pressure.
Very disappointed . It was probably something simple like needing freon....but was told it needed all this expensive parts. I am afraid to go back.
I had some cooling before the repair but nothing like it was supposed to be. I am the only owner, and it had never been recharged.
(1) Answer
Like mine, it may be a simple solution: Check your antifreeze to water mixture in your radiator. Mine was off, causing the AC to freeze up and stop the cold air from coming in. It mainly occurred when I had it set to "LOW' on the AC temp setting. I flushed the radiator, put in the correct mixture and it has worked fine since then. Hope this helps - Good Luck!!