Improper Air Delivery

If the Functional Test or other diagnosis indicates improper air delivery or a failure to shift modes when the mode knob is moved, check the attachment of all vacuum lines between the heater module and control assembly.

If the cause of the problem is not discovered, disconnect the vacuum line from the actuator at the crank pin and check the air control valve travel and effort. If there is proper valve travel and effort, check the actuator at the heater module with the vacuum hose connected and while moving the mode knob. It will be necessary to start the vehicle to assure adequate vacuum. If the actuator doesn't move, check for a broken, pinched, kinked, or otherwise damaged vacuum line or poor connection at the control assembly.