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AC works when going 1-60 MPH but not 60-80 mph, is this a vacuum problem?

I am guessing that I have a vacuum leak now, I had a mechanic check the freon and the pressure and everything is good with no leaks. So I finally figured out why MY Air Conditioner was intermittent and such,

When going from 1-50 mph or Idle or in Park the AC Is cold. But when I get on the highway and freeway and get past 65 MPH the ac starts blowing warm air, not hot but warm air as if the ac had shut off, what is this a vacuum seal problem or a tip door or blend door?

however I have read it could also be the clutch, shutting off when the rpm is real high?

Could be the evaporator freezing,I am thinking its not the speed but the time the engines been running (or the compressor) Linking warm AC to higher speed is not so common.

well see if I get back down to below 60 mph again , it will kick back on within 5 minutes.

I hope someone has an answer to this question because I have the exact same issue with a 1996 Jeep Grand Cherokee. I have been to the dealership 4 times in last 6 months with nothing found wrong. They replaced the AC and drier 10 months ago and that is when the problem started. My waranty is running out and I still have no answers.

The blend door is usually controlled by vacuum and that will go down in most cars at higher speeds. Therefor your blend door drops down to default position (heat). It could be a leak at or near the blend door or it might be somewhere else in the vacuum system. You are seeing the classic symptoms.

There is a potentially serious safety issue involved. Your power brakes are also generally run by that same vacuum system. It is possible that you could loose or have reduced power braking at the same time you are having AC problems.

I suggest you bring this to your local mechanic and have it checked out.

Joe, I think you are on the right track.