Test A: Improper/Erratic Direction Of Airflow From Outlets
WARNING: This page is about a different car, the 1999 Ford Expedition. However, it is still accessible from the selected car via links, so may be relevant.
- Check System Airflow
Start engine and run at idle. Set blower to HI speed. Turn function selector switch to each airflow position and check airflow at outlets during idle and during acceleration. If there is airflow only from defrost outlets at each switch position, go to next step. If airflow is from defrost outlets only during acceleration, go to step 19) . If airflow is incorrect under one or more conditions, go to step 13) . If airflow is correct under all conditions, system is operating properly at this time. - Check Vacuum Supply Hose Connections
Turn ignition off. Check for disconnected vacuum supply hose between intake manifold and A/C vacuum check valve. If hose is disconnected, reconnect hose and retest system. If hose is properly connected, go to next step. - Leak Check Vacuum Supply Hose
Disconnect vacuum supply hose. Connect one end to vacuum tester and plug other end. Apply vacuum and check for leaks. If hose leaks, repair or replace hose. Retest system. If hose does not leak, go to next step. - Check Vacuum Check Valve
Start engine and run at idle. Disconnect one vacuum hose at a time from check valve (remove the reservoir hose, then the control assembly source hose). Check for presence of vacuum at check valve. If vacuum is available at both check valve ports, go to step 6) . If vacuum is not available at one or both ports, go to next step. - Inspect Vacuum Check Valve
Turn ignition off. Disconnect vacuum check valve. Check for obstructions or improper operation. Airflow through check valve should be in direction of engine (marked VAC). If check valve is obstructed or plugged, replace check valve. Retest system. If check valve is okay, go to next step. - Leak Test Vacuum Check Valve
Ensure ignition is off. Disconnect vacuum check valve. Attach vacuum tester with "T" fitting and two hoses to reservoir and control assembly vacuum ports. Apply 15 in. Hg of vacuum. If vacuum leak-down exceeds 1 in. Hg per minute, remove check valve, plug test hoses and check for leakage in hoses. If hoses are okay, but leak-down exceeds 1 in. Hg per minute, replace vacuum check valve. Retest system. If leak-down did not exceed 1 in. Hg per minute, restore vacuum check valve to proper connections and go to next step. - Check Vacuum Reservoir
Disconnect hose from vacuum reservoir. With vacuum tester, check for vacuum leaks in vacuum reservoir. If reservoir leaks, replace vacuum reservoir. Retest system. If vacuum reservoir does not leak, remove hose and go to next step. - Check Function Selector Switch Vacuum Supply Hose
Disconnect vacuum supply hose from function selector switch. Connect vacuum tester to supply hose and check for vacuum leak. If function selector switch supply hose leaks, repair or replace hose. Retest system. If no vacuum leak is present, reconnect hose and go to next step. - Check Function Selector Switch
Disconnect in-line vacuum harness connector. Connect vacuum tester to Black vacuum supply hose port. Plug other hose ports. See Fig 1. As function selector switch is set to each position, apply 15 in. Hg of vacuum and watch for leak-down. If leak-down exceeds 1 in. Hg per minute, note switch position where leak-down occurred and go to next step. If leak-down does not exceed 1 in. Hg per minute, reconnect in-line vacuum harness connector and go to step 11) . - Leak Test Control Assembly
Disconnect vacuum harness from function selector switch. Connect vacuum tester to Black supply hose port on connector. See Fig 1. Plug hose port with indicated vacuum leak in previous step. Apply 15 in. Hg of vacuum. If vacuum drop exceeds 0.5 in. Hg per minute, replace function selector switch. Retest system. If vacuum drop does not exceed specified limits, reconnect function selector switch. Go to next step. - Check Vacuum Supply Hose For Blockage
Disconnect damper door switch vacuum supply hose. Attach vacuum tester to vacuum supply hose and try to pull vacuum. If tester can pull and hold vacuum, supply hose is plugged. If tester pulls vacuum that leaks down slowly, supply hose has a restriction. If Black vacuum hose is plugged or restricted replace vacuum supply hose. Retest system. If hose is not plugged or restricted, reconnect damper door switch supply hose, and go to step 15) . - Leak Test Jumper Vacuum Harness
Disconnect suspect leaking vacuum hose. Plug one end of suspect hose and attach vacuum test to other end. Apply 15 in. Hg of vacuum. If vacuum leaks, repair or replace vacuum jumper harness. Retest system. If vacuum hose does not leak, repair or replace function selector switch. Retest system. - Review Vehicle History
Turn ignition off. If airflow system functioned properly prior to current complaint, go to step 16) . If airflow system did not function properly in the past, go to next step. - Check Vacuum Motor Hoses
Disconnect function selector switch vacuum harness. Connect vacuum tester to each hose and try to pull vacuum. If vacuum can be pulled, hose is plugged or restricted. If hose is plugged or restricted, replace vacuum hose and retest system. If vacuum cannot be pulled, go to next step. - Check Vacuum Harness
Compare vacuum hose color in vacuum harness with each connector on function selector switch vacuum connector. See Fig 2 and Figure . If hose colors of vacuum harness and connector colors match, go to next step. If hose colors of vacuum harness do not match, replace vacuum harness. Retest system. - Check A/C Vacuum Circuit
Check A/C vacuum circuit for pinched or kinked vacuum hose(s). If any hose is pinched or kinked, reposition or replace hose and retest system. If hoses are okay, go to next step. - Check Vacuum Circuit Connections
Check each vacuum hose to ensure it is properly attached at all connections. See Figure. If any vacuum hose is disconnected, reconnect hose and retest system. If hoses are properly connected, go to next step. - Check Vacuum Hose
If any hose was suspect of leaks in any prior checks, disconnect suspect hose, plug one end and attach vacuum tester to other end. Apply vacuum and check for leaks. If leak exists, repair or replace hose. Retest system. If hose is okay, go to next step. - Check Vacuum Control Motor
Disconnect hose from vacuum control motor. Apply 15 in. Hg of vacuum to vacuum control motor. If vacuum drop exceeds 0.5 in. Hg per minute, replace vacuum control motor and retest system. If vacuum drop is within limits, go to next step. Reconnect vacuum control motor hose. - Check Vacuum Control Motor Installation
Check attachment of vacuum control motor to damper door. If motor arm is properly attached to damper door, service damper door for binding and retest system. If motor arm is not properly attached to damper door, connect motor arm and retest system.