97 Ram A/C question

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gliderider06

gliderider06

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My 97 Ram a/c works and blows cold when cruising, at a steafy rpm, but when I accelerate, it cuts off until back at a steady rpm. I checked the pressures and its in the ok range with my gauge, but why could it be shutting off? It is a bone stock 5.2 truck. Any ideas?
 
There is a check valve on the passenger side of the intake manifold. When you accelerate, the truck loses vacuum and the A/C needs vacuum to keep the doors open. It's usually half black and half white. Very common issue. Me my dad and my grandpa all have the same era of trucks with the same issue.
 
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Good luck finding the source, if you google "crazy vents" you'll get lots of hits. Also some years have a vacuum can under the windshield wiper housing. You have to pull the wiper arms and the black plastic cover. this area fills with water / ice sometimes and can crack the vacuum can. Also these heater/ AC units are prone to door failure in the unit. Dodge/ Chrysler should have their asses kicked for saddleing us with this junk.
 
when im on the highway and adjust ac from say floor to vent i have to let off the accellerator till the doors do thier thing then im good to go. 5.2 magnum btw
 
Thanks guys. I was able to trace the vacuum lines into the firewall and they looked good to that point. The 2 check valves are there and hooked to the intake port. I'll do some more digging around tomorrow.
Thanks, Paul
 
gliderider06 said:
Thanks guys. I was able to trace the vacuum lines into the firewall and they looked good to that point. The 2 check valves are there and hooked to the intake port. I'll do some more digging around tomorrow.
Thanks, Paul
Click to expand...

The check valves get clogged/dirty or leak internally. They're only a couple bucks. Replace them, it's worked on several trucks that I wrench on.
 
I also think there might be some "factory" restrictions in that system, and that the slightest leak might keep it from working right. These girls are "famous" for vacuum problems in the AC/heater
 
I ordered 2 check valves from Rockauto and should be in in 2 days. I will start with that first and report back.
Thanks Paul
 
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