I have an 07 G35 with 128,000 miles on it. I bought it used 18 months ago. I had problems with the ac blowing hot air sometimes and cold air at other times from the beginning. The ac condenser and radiator were replaced last summer. The freon was also recharged. The ac worked normally for awhile, then the same problem came back. It was almost winter and I didn't get around to having it looked at again until spring. I had the freon checked and recharged this spring and again, it was better for a little while. Now it is doing the same thing. Sometimes it works properly after I shut off and restart the car. Other times, I hear the compressor engage as I'm driving, and here comes the cold air... It was 99 here today, and I would love my ac to work... can you help?