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Vacuum System Test

WARNING: This page is about a different car, the 1996 Ford Explorer. However, it is still accessible from the selected car via links, so may be relevant.

Start engine. Slowly press each of following mode control (manual override) buttons, in turn: MAX A/C, VENT, PNL-FLR, FLOOR, FLR-DEF and DEF. As each button is pressed, listen for hissing sound from control panel.

A momentary hissing sound, as each button is pressed, indicates vacuum is available at control panel. If hissing sound is continuous, it indicates a large vacuum leak somewhere in system, but not necessarily at control panel. If no hissing sound is heard, check for kinked, pinched or disconnected vacuum supply hose. See VACUUM DIAGRAM. Ensure check valve between intake manifold and vacuum reservoir is functioning properly.

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