Vacuum Diagnosis - Air Delivery & Temperature Controls - HVAC System - Automatic - RPO C68

Air Delivery Vacuum Distribution Table:

VACUUM DIAGNOSIS

[!] Important:

^ To avoid misdiagnosis, perform Chart # 4, "Air Flow From Outlets is Incorrect," before beginning Vacuum Diagnosis.

1. Check vacuum supply to Solenoid Box while Engine is running.

^ Vacuum should be approximately 60 kPa (18 psi) with Engine running.
^ Vacuum should remain at approximately 60 kPa (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 malfunctioning actuator(s) as necessary.
3. Reconnect all vacuum and electrical connections. Run Engine and cycle through the operating modes of the HVAC Control Assembly while observing the vacuum actuators.

^ Check for vacuum to the vacuum actuators by noting vacuum actuator. position. When vacuum is applied, the actuator will retract, refer to Air Delivery Vacuum Distribution Table.
^ If a vacuum actuator retracts when it should not, replace the HVAC Control Assembly.
^ If a vacuum actuator does not retract when it should, check for vacuum leaks, collapsed vacuum hoses, binding valves or bad connections at the Solenoid Box. If OK, replace the Solenoid Box.