Grand Cherokee 4WD Laredo V8-4.7L (2002)
Vacuum Check Valve HVAC: Description and Operation
Two vacuum check valves (non AZC only) are installed on the vacuum supply system One is on the accessory vacuum supply line in the engine
compartment, near the vacuum tap on the engine intake manifold. A second vacuum check valve is located on the bottom of the HVAC unit behind the
passenger front floor duct on the black vacuum line. The vacuum check valves are 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 A/C Heater mode settings. The check valve will
prevent the engine from bleeding down system vacuum through the intake manifold during extended heavy engine load (low engine vacuum) operation.
The vacuum check valve cannot be repaired and, if faulty or damaged, it must be replaced.
