2005 a/c problems

[Jesus Freak]

My in-laws Expedition has been giving them A/C fits. They describe the problem as follows: After driving 70-75 mph for 45 mins to an hour the a/c quits working. They can turn it off for about an hour, and it begins to work again. At speed of 60mph or less, they have never had a problem w/ the a/c.

 

[JUST4FUN]

mabey the evaperator is freezing up or its low on 134a

 

[Jesus Freak]

They had the car checked by a mechanic, who in my estimation, is incompetent in a/c repair. He couldn't find anything. What would cause the evaporator to freeze up? Thanks!

 

[JUST4FUN]

well a blocked drain in the evap case,dose the air stop blowing out the regesters all together?