Cherokee 4WD L6-4.0L VIN S (1998)
Vacuum Check Valve HVAC: Description and Operation
Vacuum Check Valve
A vacuum check valve is installed in the accessory vacuum supply line in the engine compartment, near the vacuum tap on the engine intake
manifold. 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 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.
