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A/c-Heater System Diagnosis - Automatic Ford LTD Crown Victoria I

Automatic HVAC System 2 illustrations ~1030 words

Error Code Test Table (1 of 2). Scheme 16

Scheme 16: Error Code Test Table (1 of 2)
Scheme 16: Error Code Test Table (1 of 2)

Error Code Test Table (2 of 2). Scheme 17

Scheme 17: Error Code Test Table (2 of 2)
Scheme 17: Error Code Test Table (2 of 2)

AUTOMATIC TEMPERATURE CONTROL

Note. Prior to testing, run engine until it reaches operating temperature. Interior of vehicle should be between 75-80°F (24-27°C). Perform all ATC tests with engine running above 1,200 RPM.

Insufficient Or No Heat

Set temperature lever to 85°F. Check vacuum at servo. If vacuum is 3 in.Hg or lower, check for hot heater hoses to and from heater core and that servo holds blend door in full heat position. If vacuum is over 3 in.Hg, disconnect line from servo and note heater output temperature. If heater output is okay, check sensor cable adjustment. If sensor cable is okay, replace sensor.

Insufficient Or No Cooling

Set temperature lever to 65°F. Check vacuum at servo. If vacuum is 12 in.Hg or greater and there is no cooling, check refrigerant circuit and recirc door circuit. If vacuum is under 12 in.Hg, check sensor cable adjustment. If sensor cable is okay, check for vacuum at sensor. If vacuum is available, replace sensor.

Discharge Temperature Rises On Acceleration

Check vacuum at servo while engine is under load. If vacuum drops, check for vacuum leak or inoperative check valve.

Note. A severe vacuum leak will cause air distribution to change to DEFROST mode.

Long Periods Of Heat, Then Long Periods Of Cooling

Sensor not sampling interior air. Check for blocked or pinched aspirator hose.

Long Periods Of Cooling, Then Long Periods Of Heat

Sensor not sampling interior air. Check for blocked or pinched aspirator hose.

Discharge Temperature Too Hot In Cold Ambient Temperature

Sensor is sampling ambient temperature only. Check for blocked sensor exhaust port.

Discharge Temperature Too Cold In High Ambient Temperature

Sensor is sampling ambient temperature only. Check for blocked sensor exhaust port.

Sensor Buzzes

Sensor output is blocked or pinched.

Heating & Cooling Okay, But Settles Out Too Warm Or Cool

Sensor is out of adjustment, malfunctioning or sensor-to-instrument panels not sealing.

SELF-TEST SYSTEM

Note. To ensure accurate self test results, this procedure must be followed first before entering SELF-TEST MODE test.

The control panel head has a self test feature that aids in locating trouble in the EATC system. To get reliable results perform the following procedure

  1. Turn on ignition. Set control panel to 90° and press "OFF" mode button. Wait 40 seconds. If VFD begins to flash, there is a malfunction in the continuous position actuator wiring harness, actuator or control panel.
  2. If LED begins to flash, a malfunction exists in one of 2 other position actuator wiring harnesses, actuators or control panel.
  3. If no flashing occurs, set control panel to 60° and press "DEFROST" mode button. Wait 40 seconds and look for a flashing VFD or LED. If no flashing occurs, then no malfunctions in the actuator drive or feedback circuits have been detected.
  4. Whether or not flashing has occurred, proceed to SELF-TEST MODE for further diagnostic information.

SELF-TEST MODE

  1. To enter self-test mode, press "OFF" and "DEFROST" mode buttons at the same time. Within 2 seconds, press "AUTO" mode button.
  2. If an 88 is displayed on control panel, no malfunctions have been detected. If a control panel detectable malfunction has occurred, the appropriate error code will be displayed. See ERROR CODE TEST table.
  3. The error code sequence will continue until "COOLER" button is pushed. When "COOLER" button is pushed, system will revert to the "AUTO" mode at a temperature setting one less than setting before entering the self test mode.
  4. Always exit self test mode by pushing "COOLER" mode button before turning off ignition. This step will ensure proper resetting of control panel when ignition is turned on.

HISSING ATC VACUUM SYSTEM OR MODE SELECTION VALVE

  1. Check in-line and control panel multiple connectors for proper installation. If hiss continues, go to step 2). If hiss stops, recheck system operation.
  2. Move mode lever to determine which positions leak. If all leak, go to next test. If some but not all leak, go to step 3).
  3. Pinch off suspect tubes one at a time near each respective vacuum motor. If hiss continues, go to step 4). If hiss stops, check tube connection to vacuum motor, and repair or reconnect. If hiss continues, replace vacuum motor.
  4. Pinch off suspect tubes one at a time near control assembly and/or in-line connector. If hiss stops, check and repair tube. If hiss continues, replace mode selector valve.

ALL MODE SELECTOR VALVE POSITIONS LEAK

  1. Move temperature control lever from 65° to 85°. If hiss stops at some settings, go to next test. If hiss continues, check Black vacuum source tube from reservoir to control assembly for cuts or disconnection and repair if necessary.
  2. If no problem is found, pinch off source tube at control assembly. If hiss stops, replace selector valve.
  3. If hiss continues, pinch off source tube at diverter valve. If hiss stops, replace servo assembly. If hiss continues, pinch off source tube at TBL switch.
  4. If hiss stops, replace TBL switch. If hiss continues, pinch off source tube at ATC sensor.
  5. If hiss stops, go to step 6). If hiss continues, recheck source tube connections, reservoir and check valve.
  6. Pinch off Tan tube at ATC sensor. If hiss stops, go to step 7). If hiss continues, replace ATC sensor.
  7. Pinch off Tan tube at servo motor. If hiss stops, replace servo motor. If hiss continues, repair tube.

SOME TEMPERATURE CONTROL LEVER POSITIONS LEAK

  1. Pinch off Black source tube at diverter valve. If hiss stops, go to step 3). If hiss continues, pinch off Black source tube at ATC sensor.
  2. If hiss stops, go to step 4). If hiss continues, recheck source tubes, connections, reservoir and check valve.
  3. Pinch off Purple tube at diverter valve. If hiss stops, go to step 5). If hiss continues, replace servo assembly.
  4. Pinch off Tan tube at ATC sensor. If hiss stops, go to step 6). If hiss continues, replace ATC sensor.
  5. Pinch off Purple tube at control panel. If hiss stops, replace selector valve. If hiss continues, repair tube.
  6. Pinch off Tan tube at servo motor. If hiss stops, replace servo motor. If hiss continues, replace tube.

See also:
• SELF-TEST MODE

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