F 350 2WD Pickup V8-460 7.5L VIN G EFI (1997)
Vacuum Harness HVAC: Testing and Inspection
Mini-Tube Vacuum Hoses
To check for proper functional control in the system, move the heater blower motor switch to HIGH. Then, move the function selector to each of its
seven positions. There should be airflow from the appropriate registers, heater outlet floor duct and nozzles and no airflow in the OFF position.
If proper airflow is not provided, look for the following:
^
An A/C plenum vacuum harness that is not fully seated at the vacuum control motor.
^
A damaged connector between the A/C control and heater air plenum chamber.
^
A damaged connection between the heater air plenum chamber and vacuum source.
^
An A/C plenum vacuum harness that is pinched or trapped.
^
A transposed vacuum line (evident when the color code on the vacuum line fails to match the color code on its mating vacuum nipple).
^
An inoperative A/C control.
