Troubleshooting Hints - Air Delivery

TRY THE FOLLOWING CHECKS BEFORE DOING THE SYSTEM DIAGNOSIS:
1. Check for manifold vacuum to the Vacuum Tank at the BLACK hose.
- If vacuum is present at the Vacuum Tank, check for vacuum at the VIOLET hose at the Heater and A/C Control Assembly. If there is no vacuum, check the VIOLET hose. If the vehicle is equipped with Cruise Control, check the BLACK hose to the Cruise Control Servo. If the hose is good, replace the Vacuum Tank.
2. Check the operation of the Temperature Valve by moving the temperature selector rapidly back and forth several times. Listen for the valve to strike the stop at each end of its travel. If the sound indicates that the valve is not fully closing or opening, check the mechanical linkage between the valve and the temperature selector.
- Go to the HVAC System Check for a guide to normal operation and diagnostic references. System Check - Overall