RAM 2500 Truck 4WD V10-8.0L VIN W (1997)
Vacuum Check Valve HVAC: Description and Operation
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 he repaired and, if faulty or damaged, it must be replaced.
