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Test O: Temperature Control Inoperative Using Front/Rear Auxiliary Controls

WARNING: This page is about a different car, the 2001 Ford Expedition and 2000 Ford Expedition. However, it is still accessible from the selected car via links, so may be relevant.
  1. Turn ignition on. Turn front auxiliary blower switch to HI position. Rotate front auxiliary temperature control from COOL to WARM. If front auxiliary control operates properly, go to next step. If front auxiliary control does not operate properly, go to step  8.
  2. Turn front auxiliary blower motor switch to REAR position. Turn rear auxiliary blower motor switch to HI position. Rotate rear auxiliary temperature control from COOL to WARM. If rear auxiliary control operates properly, system is okay at this time. If control does not operate properly, go to next step.
  3. Turn ignition off. Disconnect rear auxiliary blend potentiometer 3-pin harness connector. Disconnect auxiliary climate control module 10-pin harness connector C436. Measure resistance of Yellow wire between rear auxiliary potentiometer connector and auxiliary climate control module harness connector C436 terminal No. 2. See Figure and Figure . Measure resistance between ground and auxiliary climate control module harness connector C436 terminal No. 2 (Yellow wire). If resistance between connectors is less than 5 ohms and more than 10 k/ohms between connector and ground, go to next step. If resistances are not as specified, repair Yellow wire as necessary. See WIRING DIAGRAMS . Recheck system operation.
  4. Disconnect rear auxiliary blend actuator 8-pin harness connector C435. Measure resistance of White wire between rear auxiliary blend potentiometer harness connector terminal No. 3 and auxiliary blend actuator harness connector C435 terminal No. 6. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open or high resistance in White wire. See WIRING DIAGRAMS . Recheck system operation.
  5. Measure resistance of Brown wire between rear auxiliary blend potentiometer harness connector terminal No. 1 and auxiliary blend actuator harness connector C435 terminal No. 4. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open or high resistance in Brown wire. See WIRING DIAGRAMS . Recheck system operation.
  6. Measure resistance between rear auxiliary blend potentiometer terminals No. 1 and 3. See Figure. If resistance is between 4-6 k/ohms, go to next step. If resistance is not between 4-6 k/ohms, replace rear auxiliary blend potentiometer. Recheck system operation.
  7. Measure resistance between rear auxiliary blend potentiometer terminals No. 1 and 2 while rotating potentiometer. See Figure. If resistance varies, replace auxiliary climate control module. Recheck system operation. If resistance does not vary, replace rear auxiliary blend potentiometer. Recheck system operation.
  8. Turn front auxiliary blower motor switch to REAR position. Turn rear blower switch to HI position. Rotate auxiliary temperature control from COOL to WARM. If rear temperature control operates properly, go to next step. If control does not operate properly, go to step  14.
  9. Turn ignition off. Disconnect front auxiliary blend potentiometer 3-pin harness connector. Disconnect auxiliary climate control module 10-pin harness connector C436. Measure resistance of Red wire between front auxiliary mode potentiometer harness connector terminal No. 2 and auxiliary climate control module harness connector C436 terminal No. 5. See Figure and Figure . Measure resistance of Red wire between auxiliary climate control module connector and ground. If resistances between connectors is less than 5 ohms and more than 10 k/ohms between connector and ground, go to next step. If resistances are not as specified, repair Red wire as necessary. See WIRING DIAGRAMS . Recheck system operation.
  10. Disconnect front auxiliary blend actuator 8-pin harness connector C435. Measure resistance of White wire between front auxiliary blend actuator potentiometer harness connector terminal No. 3 and auxiliary blend actuator harness connector C435 terminal No. 6. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open or high resistance in White wire. See WIRING DIAGRAMS . Recheck system operation.
  11. Measure resistance of Brown wire between front auxiliary blend actuator potentiometer harness connector terminal No. 1 and auxiliary blend actuator harness connector C434 terminal No. 4. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open or high resistance in Brown wire. See WIRING DIAGRAMS . Recheck system operation.
  12. Measure resistance between front auxiliary blend actuator potentiometer terminal No 1 and 3. See Figure. If resistance is between 4-6 k/ohms, go to next step. If resistance is not between 4-6 k/ohms, replace front auxiliary blend actuator potentiometer. Recheck system operation.
  13. While rotating potentiometer, measure resistance between front auxiliary blend actuator potentiometer terminals No 1 and 2. See Figure. If resistance varies, replace auxiliary climate control module. Recheck system operation. If resistance does not vary, replace front auxiliary blend actuator potentiometer. Recheck system operation.
  14. Turn ignition off. Disconnect auxiliary blend actuator 8-pin harness connector C435. Turn ignition on. Measure voltage between ground and auxiliary blend actuator harness connector C435 terminal No. 7 (White/Light Blue wire). If more than 10 volts exists, go to next step. If 10 volts or less exists, repair open in White/Light Blue wire. See WIRING DIAGRAMS . Recheck system operation.
  15. Turn ignition off. Measure resistance between ground and auxiliary blend actuator harness connector C435 terminal No. 8 (Black wire). If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open or high resistance in Black wire. See WIRING DIAGRAMS . Recheck system operation.
  16. Measure resistance of Light Blue wire between auxiliary blend actuator harness connector C435 terminal No. 3 and auxiliary climate control module harness connector C436 terminal No. 2. Measure resistance between ground and auxiliary blend actuator harness connector C435 terminal No. 3 (Light Blue wire). If resistances between connectors is less than 5 ohms and more than 10 k/ohms between connector and ground, go to next step. If resistances are not as specified, repair Light Blue wire as necessary. See WIRING DIAGRAMS . Recheck system operation.
  17. Disconnect front auxiliary blend potentiometer 3-pin harness connector. Disconnect rear auxiliary blend potentiometer 3-pin harness connector. Measure resistance of White wire between auxiliary blend actuator harness connector C435 terminal No. 6 and rear auxiliary blend potentiometer harness connector terminal No. 3. Measure resistance between ground and auxiliary blend actuator harness connector C435 terminal No. 6 (White wire). If resistances between connectors is less than 5 ohms, and more than 10 k/ohms between connector and ground, go to next step. If resistances are not as specified, repair White wire as necessary. See WIRING DIAGRAMS . Recheck system operation.
  18. Measure resistance of Brown wire between auxiliary blend actuator harness connector C435 terminal No. 4 and rear auxiliary blend potentiometer harness connector terminal No. 1. Measure resistance between ground and auxiliary blend actuator harness connector C435 terminal No. 4 (Brown wire). If resistances between connectors is less than 5 ohms, and more than 10 k/ohms between connector and ground, go to next step. If resistances are not as specified, repair Brown wire as necessary. See WIRING DIAGRAMS . Recheck system operation.
  19. Measure resistance between ground and auxiliary climate control module harness connector C436 terminal No. 9 (Yellow wire). If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open or high resistance in Yellow wire. See WIRING DIAGRAMS . Recheck system operation.
  20. Measure resistance between ground and auxiliary climate control module harness connector C436 terminal No. 5 (Red wire). If resistance is more than 10 k/ohms, go to next step. If resistance is 10 k/ohms or less, repair short to ground in Red wire. See WIRING DIAGRAMS . Recheck system operation.
  21. Reconnect auxiliary blend actuator connector. Turn ignition on. Turn front auxiliary blower switch to HI position. Connect jumper wire between auxiliary climate control module harness connector C436 terminals No. 2 (Light Blue wire) and No. 8 (White/Light Blue wire). If auxiliary blend actuator operates, replace auxiliary climate control module. Recheck system operation. If actuator does not operate, go to next step.
  22. Connect jumper wire between auxiliary climate control module harness connector C436 terminal No. 2 (Light Blue wire) and No. 6 (Black wire). If auxiliary blend actuator operates, replace auxiliary climate control module. Recheck system operation. If actuator does not operate, replace auxiliary blend actuator. Recheck system operation.
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