Vacuum System Diagnosis - HVAC System - Manual

Ai Delivery Vacuum Distribution Table:

Air Delivery Vacuum Distribution

Important: To avoid misdiagnosis, complete Functional Check before beginning vacuum diagnosis.

1. Check vacuum supply to vacuum/electric solenoid (purple and black vacuum hoses) while engine is running.
- Vacuum should be approximately 60kPa (18 psi) with engine running.
- Vacuum should remain at approximately 60kPa (18 psi) when 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. Run engine and cycle through the operating modes of the heater-A/C control while observing the valve actuators.
- Check for vacuum to the mode valve actuators by noting 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. Refer to Control Assembly Replacement for repair procedures. Control Assembly
- If a vacuum actuator does not retract when it should, check for vacuum leaks, collapsed vacuum hoses or binding valves. If OK, replace the vacuum/electric solenoid.