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Both heater and A/C in your Navigator are controlled by the control head. As such, the recommended first diagnostic step is the retrieval of any trouble codes that may be stored in its memory. To do so, please follow the procedure shown below:
ELECTRONIC AUTOMATIC TEMPERATURE CONTROL MODULE SELF-TEST
The EATC module self-test will not detect concerns associated with data link messages like engine coolant temperature or vehicle speed signals. A New Generation Start (NGS) tester, or equivalent aftermarket scan tool, must be used to retrieve these concerns.
The EATC module self-test will detect concerns in the system control functions and will display hard diagnostic trouble codes (DTC) in addition to intermittent diagnostic trouble codes for concerns that occur during system operation. The vehicle interior temperature should be between 4°-32°C (40-90°F) when performing the self-test. If the temperatures are not within the specified ranges, false in-car temperature sensor DTCs will be displayed.
The self-test can be initiated at any time. Normal operation of the system stops when the self-test is activated.
1. To enter the self-test, press the OFF and FLOOR buttons simultaneously and then press the AUTOMATIC button within two seconds. The display will show a pulse tracer going around the center of the display window. The test may run as long as 30 seconds. Record all DTCs displayed.
2. If any DTCs appear during the self-test, follow the diagnostics procedure given under ACTION for each DTC given.
3. If a condition exists but no DTCs appear during the self-test, go to TEST B: EATC SYSTEM IS INOPERATIVE, INTERMITTENT OR IMPROPER OPERATION under SYMPTOM TESTS.
4. To exit self-test and retain all intermittent DTCs, push the blue (cooler) button. The control will exit self-test, retain all intermittent diagnostic trouble codes and then turn OFF (display blank).
5. To exit self-test and clear all diagnostic trouble codes, press the DEFROST button. The vacuum fluorescent display window will show 888 and all function symbols for one second. Then, the EATC control assembly will turn OFF (display blank) and all DTCs will be cleared.
6. Always exit the self-test before powering the system down (system turned OFF).
7. Intermittent DTCs will be deleted after 80 ignition switch ON cycles after the intermittent condition occurs.
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