Vacuum & AC suck under tha bridge

What connection is there between the vacuum system and the ac that would let the air stop blowing out into the cabin after about 90 min running on the
interstate highway system at continuous speed of about 65 to 75 miles/hour? Shoud such a device have been replaced when the evaporator was replaced about a month ago?
mcbrue wonderingly under the bridge in the trailer down by the river
96 S420
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Just a wild guess, but I'd look for a soft vacuum hose that collapses due to the suction whenever it gets soft enough from the heat. I used to lose the power assist to my brakes on my old Caddy due to a collapsed vacuum hose whenever it would get hot. If the problem 'heals' itself again once it has a chance too cool down overnight, I'd almost guarantee that's what you'll find.
Jerry Wolfram '78 450 SL - 212K miles
MCBRUE wrote:

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snipped-for-privacy@aol.com (MCBRUE) wrote in message

I think you might be happier if you just bought a new one.
Its only money. They print more every day.
.
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