Air conditioner problem

[Ebsorny]

I just had my AC recharged and it is blowing cold air. However it's only blowing through the defrost at in town driving speeds(up to roughly 45 mph). Once at highway speeds(45 mph and up) it starts blowing through the dash vents where it's supposed to. Any ideas on what would cause this?

 

[koda2000]

You have a vacuum leak somewhere. This causes the air to come out of only the defroster vents any time you put the engine under a load. Even a tiny leak will cause this. Start by checking the lines under the hood.

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