Troubleshooting Hints

Try the following checks before performing other diagnosis.

1. Check for manifold vacuum to the Vacuum Tank at the BLACK hose from the engine.

^ If vacuum is not present, check the hose back to the Engine Intake Manifold Tap.
^ If vacuum is present at the Vacuum Tank, check for vacuum at the VIOLET hose of the Heater-A/C Control Assembly. If there is no vacuum, check the VIOLET hose. If the hose is good, replace the Vacuum Tank.

2. Check the operation of the Temperature Valve by moving the Temperature Lever rapidly back and forth several times. Listen for the door to strike the stop at each end of its travel. If the sound indicates that the door is not fully closing or opening, check the mechanical linkage between the Valve and the Temperature Lever.