I have also run into the summer AC problems with the air coming out of the defrost vents when under load. I have read many posts that one major cause is the vaccuum lines under the battery tray. I have removed the 4 bolts that sit under and beside the battery, however I still can not get the tray out to inspect the lines. Please help a old man / newbie out. Thanks to everyone that keeps this sight up and running, it has been very helpful!!

1997 Ram 1500 4X4 5.2

 

If the a/c is losing vacuum, the only way the cruise would effect it is if the 2nd check valve is faulty. It's the one near the pass. side firewall incorporated in a tee. It's function is to stop the cruise control from bleeding off vacuum and causing the a/c to draw down. If you have lost a/c function completely, check all the tubes from the manifold back to the firewall for leaks. If it only happens under load, suspect a faulty check valve. If cruise is acting up, then, yes check all those lines as well.
WC

 

VACUUM CHECK VALVE
A one-way vacuum check valve is installed in the accessory vacuum supply line near the vacuum tap on the right side of the engine intake manifold. This check valve helps to maintain the system vacuum needed to retain the selected heater-A/C mode and vehicle speed control settings. It prevents the engine from bleeding down system vacuum through the intake manifold during extended heavy engine load (low engine vacuum) operation.
A second one-way vacuum check valve is installed in the accessory vacuum supply line at the tee fitting near the dash panel in the engine compartment. This valve also helps to maintain the system vacuum needed to retain the selected heater-A/C mode settings, but isolates the heater-A/C vacuum circuit from the vehicle speed control vacuum circuit. It prevents the vehicle speed control servo from bleeding down the heater-A/C system vacuum during extended heavy engine load operation.
The vacuum check valve cannot be repaired and, if faulty or damaged, it must be replaced.
VACUUM RESERVOIR
The vacuum reservoir is mounted in the right cowl plenum area, under the cowl plenum cover/grille panel. Vacuum stored in the reservoir is used to operate the vacuum-controlled vehicle accessories during periods of low engine vacuum, such as when the vehicle is climbing a steep grade or under other high engine load operating conditions.
The vacuum reservoir cannot be repaired and, if faulty or damaged, it must be replaced.
[*]Disconnect and isolate the battery negative cable.[*]Remove the windshield wiper arms from the wiper pivots. Refer to Wiper and Washer Systems for the procedures.[*]Remove the weatherstrip along the front edge of cowl plenum cover/grille panel Cowl Plenum Cover/Grille Panel Weatherstrip[*]Release the plastic anchor screws Plastic Anchor Screws Remove/Install[*]Lift the cowl plenum cover/grille panel from the vehicle far enough to access the vacuum reservoir.[*]Unplug the vacuum supply line from the vacuum reservoir Vacuum Reservoir Remove/Install[*]Remove the two screws that secure the reservoir to the right side of the cowl plenum panel.[*]Remove the vacuum reservoir.[*]Reverse the removal procedures to install.[*][/ol]

 

WayneC and Parts/Service

Thank you for your help =]