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A/C System Performance

WARNING: This page is about a different car, the 1994 Mercury Grand Marquis and 1994 Ford Crown Victoria. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: Perform A/C system performance test when reasonably certain that A/C system (compressor, etc.) is okay and interior temperature is 70-80°F (21-27°C).
  1. Blower Motor Operation  Ensure interior temperature is 70-80°F (21-27°C). Ensure blower motor leads are connected and A/C 3 fuses in instrument panel fuse box are good. Verify battery voltage exists at control module terminal No. 10 (Light Green/Yellow wire). Verify battery voltage from A/C damper door switch exists at control module terminal No. 11 (Orange wire). If blower motor operates, go to next step. If blower motor does not operate, see TROUBLE SHOOTING section.
  2. Blower Function  Ensure A/C blower motor and blower motor controller connections are clean and tight. If blower motor operates in AUTO, or from LOW to HIGH, go to next step. If blower motor does not operate in AUTO, or from LOW to HIGH, see TROUBLE SHOOTING section.
  3. Air Discharge Locations  Check for incorrect or erratic air discharge locations. If air discharge operates correctly, go to next step. If air discharge locations are erratic or incorrect, check for leaking or disconnected vacuum lines. Check for leaking, damaged or inoperative vacuum motors and/or valves. Repair or replace as necessary.
  4. A/C Blower Motor Speed  Operate system. Select different blower speeds. Verify wiring continuity in Yellow/Red wire, Light Green/White wire and Light Blue/Orange wire between blower motor speed controller connector and control module connector. If blower motor speed varies according to switch position, go to next step. If blower motor stays in high speed in all switch positions, see TROUBLE SHOOTING section.
  5. Discharge Air Temperature  Operate system. Set blower motor switch in AUTO position. If discharge air temperature varies with change in temperature lever position, go to next step. If discharge air temperature does not vary, check connections at blend door actuator. Ensure continuity exists in White/Yellow wire between electronic door actuator motor and control module connector. Ensure continuity exists in Purple wire between electronic door actuator motor and control module connector. Repair wire(s) as necessary.
  6. A/C Blower Motor Speed  Operate system. Change temperature lever positions. If blower motor speed changes with temperature lever position, go to next step. If blower speed does not change with temperature lever position, see BLEND DOOR ACTUATOR.
  7. Discharge Air Temperature Hot  Operate system with blower switch in AUTO. If discharge air temperature does not remain at full heat when temperature lever position is changed, go to next step. If discharge air temperature remains at full heat at all temperature lever positions, ensure automatic temperature control sensor connector and hose are connected. Ensure continuity exists in White/Orange wire between automatic temperature control sensor and control module connector. Ensure continuity exists in Pink/Black wire between automatic temperature control sensor and control module connector. Repair wire(s) as necessary.
  8. Blower Motor Speed  Set blower motor control to maximum speed. If blower motor does not operate at maximum speed, go to next step. If blower operates at maximum speed, ensure ambient air temperature sensor connection is clean and tight. Ensure continuity exists in Light Blue/Orange wire between ambient air temperature sensor and control module connector. Ensure continuity exists in Pink/Black wire between ambient air temperature sensor and control module connector. Repair wire(s) as necessary.
  9. Operate System With Blower Switch In AUTO Position  Verify blower motor speed remains unchanged when temperature control lever is moved slowly from 65 to 85°F. Ensure discharge air temperature changes. If discharge air temperature does not change when temperature control lever is moved, go to next step. If discharge temperature changes, ensure automatic air control temperature sensor connection is clean and tight. Ensure continuity exists in White/Orange wire between automatic air temperature control sensor and control module connector. Ensure continuity exists in Pink/Black wire between automatic air temperature control sensor and control module connector. Repair wire(s) as necessary.
  10. Set Temperature Selector Lever 72-78°F (22-26°C)  If blower motor speed does not oscillate rapidly or change constantly, go to next step. If blower motor speed oscillates rapidly or changes constantly, ensure ambient air temperature sensor connection is clean and tight. Ensure continuity exists in Light Blue/Orange wire between ambient air temperature sensor connector and control module connector. Repair wire as necessary.
  11. Change Blower Motor Speed Setting  If blower motor speed changes, go to next step. If blower motor speed does not change, see TROUBLE SHOOTING section.
  12. System Operation  Change blower motor speed setting. If system operates correctly and reaches maximum heating or cooling, go to next step. If system does not operate properly, check Yellow/White wire and Light Green/Yellow wire at control module connector for loose or corroded connections. Repair connections as necessary. Disconnect negative battery cable for 2 minutes to allow system to recalibrate. Retest system.
  13. Function Selection Operation  Ensure engine coolant temperature is greater than 120°F (49°C). Set function lever to FLOOR position. If there is air output at floor position, go to next step. If there is no air output at floor position, ensure engine coolant level is correct. Check Light Blue/Orange wire between control module and temperature control lock-out valve and switch for continuity. Repair wire as necessary.
  14. Temperature Control Lock-Out Valve & Switch Operation  Ensure engine coolant temperature is greater than 120°F (49°C). Set function lever to FLOOR position. If there is no air output at floor position at any time, go to next step. If there is air output at floor position at all times, see TROUBLE SHOOTING section.
  15. Blower Motor Operation  Set blower motor switch to OFF position. If blower motor stops operating, go to next step. If blower motor continues to operate, check Orange/Black wire between blower motor speed controller connector and blower motor connector for short circuit to battery voltage. Repair wire as necessary. If wire is good, check blend door actuator for damage. Replace actuator if necessary.
  16. System Temperature Operation  Operate system. If system alternates between long periods of heating and cooling, ensure automatic temperature control sensor hose and elbow are connected in dash. Ensure hose and elbow are free of blockages and kinks. Repair hose and elbow as necessary. If system does not alternate between long periods of heating and cooling, functional testing is completed.
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