Important: In order to avoid misdiagnosis, complete Diagnostic System Check before beginning the vacuum diagnosis.

1. Test the vacuum supply to the vacuum/electric solenoid (purple and black vacuum hoses) while the engine is running.

•	Vacuum should be approximately 60 kPa (18 psi) with the engine running.

•	Vacuum should remain at approximately 60 kPa (18 psi) when the engine is turned OFF.

2. Test each vacuum actuator by disconnecting the vacuum hose and applying vacuum directly to the actuator. Repair or replace as necessary.
3. Reconnect all vacuum and electrical connections. Start the engine and cycle through the operating modes of the heater-A/C control while observing the valve actuators.

•	Test for vacuum to the mode valve actuators by noting the mode valve actuator position. When vacuum is applied, the actuator will retract, refer to the Air Delivery Vacuum Distribution table.

•	If a vacuum actuator retracts when it should not, replace the heater-A/C control module assembly. Refer to Control Assembly Replacement in Instrument Panel, Gauges and Console for service procedure.

•	If a vacuum actuator does not retract when required, inspect for vacuum leaks, collapsed vacuum hoses, or binding valves. If OK, replace the vacuum/electric solenoid.