RAM 2500 Truck 4WD L6-5.9L DSL Turbo VIN 6 (1999)
Vacuum Check Valve HVAC: Description and Operation
SYSTEM OPERATION
A vacuum check valve is installed on the engine vacuum pump. The vacuum check valve is designed to allow vacuum to flow in only one direction
through the accessory vacuum supply circuits.
The use of a vacuum check valve helps to maintain the system vacuum needed to retain the selected heater-A/C mode and vehicle speed control
settings. It prevents oil from contaminating the vacuum supply system by maintaining vacuum in the pump after engine shut-off.
The vacuum check valve cannot be repaired and, if faulty or damaged, it must be replaced.
