Dodge: a/c, dodge ram 1500, vacuum line

Question
exactly thats what it does,, it goes to a defrost mode thru the dash vent.i shoulda mentioned that the first time. i am certain its not compressor related cuz it blows very cool and doesn't turn on an off as if there was low freon.i was told there is some sorta inline vacuum valve thats easily accesible to change out.

at 15k miles the fuel pump went out, 37k miles power sterring pump went out, and at 39k miles a/c evaporator went out. this is definatley my last dodge i ever buy. i have to say, the truck handles very nice, just too many repairs at so little miles.
thanks for all your help
Mark
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Followup To
Question -
I HAVE A 97 DODGE RAM 1500 TRUCK. 45K MILES. ALREADY REPLACED A/C EVAPORATOR 2 YEARS AGO. MY PROBLEM IS WHEN I ACCELLERATE AND THE RPMS INCREASES THE A/C SHUTS OFF, THEN TURNS BACK ON WHEN RPMS GOES DOWN. ANY IDEAS WHY IT DOES THIS?
Answer -
Mark,
It sounds like the issue is with the A/C compressor.Normally it will kick on and off but it shouldn't be doing it so rapidly.It is normal for the compressor to come on and off but shouldn't have anything to do with you letting off the accelerator.I'd let an a/c man look at the compressor and explain to him what it's doing.Something as simple as a vacuum leak will cause these sort of symptoms but it usually results in you noticing the inside vents on the dash to change to the defrost vent.A/C work needs to be checked by a certified technician due to the freon in the compressor.

Answer
Yes it is called a check valve and goes on the vacuum line that goes into the firewall on the passenger side.This vacuum line also hooks to your servo under the battery.When you install this it will solve your problems.I've had the same problem with mine.