Vacuum Check Valve HVAC: Description and Operation

A vacuum check valve is installed in the vacuum supply line in the vacuum harness. The check valve is located near the left end of the distribution duct under the instrument panel in the passenger compartment. The vacuum check valve is designed to allow vacuum to flow in only one direction through the 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.