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The doors in the HVAC box that direct the air are vacuum operated. They are designed such that if vacuum is lost, the airflow defaults to the lower (heater) ducts and the defroster duct. The cause of your problem could be as simple as a vacuum hose that got knocked off (like the one that goes to the intake manifold that provides the vacuum source) or a bad vacuum actuator that operates the doors. The only way to figure this out is to crack open the Chassis Service Manual, turn to the page in the air conditioning section that shows the hose routing, and trace the hoses until you find where the problem is.
Also, it is neither necessary nor in your best interest to post the same question in multiple threads. Keeping all responses in one place will get you a better answer more quickly.
As Joe noted above, there is a vacuum hose that connects from the intake manifold behind the carburetor the the vacuum reservoir on the firewall, then a hose that goes from the reservoir through the firewall to the AC controls.
Here's a picture showing where the reservoir is located:
South L:ouisiana 1971 cutlass Supreme
May 10th, 2024, 01:20 AM
