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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> Heating, Ventilation & A/C (HVAC) >> HVAC Control Systems >> Heater Systems >> Symptom Tests >> Test "D": Blower Motor Malfunction

Test "D": Blower Motor Malfunction

NOTE: For circuit reference, see CONNECTOR IDENTIFICATION  and/or WIRING DIAGRAMS  .
NOTE: Definition: The blower motor operates in at least one, but not all, speed positions.
  1. Did you perform the HVAC DIAGNOSTIC SYSTEM CHECK? If so, go to next step. If not, see DIAGNOSTIC SYSTEM CHECK  under TROUBLE SHOOTING.
  2. Turn the ignition on, with the engine off. Place the mode control in the VENT position. Place the blower motor switch in each speed position. Does the blower motor operate in each speed position? If so, go to next step. If not, go to step  4.
  3. Place the blower motor switch in the maximum speed position. Place the mode control in each position. Does the blower motor operate in each position? If so, problem is intermittent. See SYMPTOM DIAGNOSIS  under TROUBLE SHOOTING. If not, go to step  18.
  4. Turn the ignition off. Disconnect the blower motor. Turn the ignition on, with the engine off. Connect a test light from ground to the blower motor supply terminal ("A"). Place the blower motor switch in each speed position. Does the test light illuminate in each speed position? If so, go to step  16. If not, go to next step.
  5. Does the test light illuminate in the maximum speed position? If so, go to step  10. If not, go to next step.
  6. Turn the ignition off. Disconnect the blower motor relay. Turn the ignition on, with the engine off. Connect a test light from ground to the battery voltage circuit (Orange wire) of the blower motor relay. Does the test light illuminate? If so, go to next step. If not, go to step  19.
  7. Place the blower motor switch in the maximum speed position. Probe the high blower motor control circuit of the blower motor relay with a test light that is connected to ground. Does the test light illuminate? If so, go to step  9. If not, go to next step.
  8. Check the high blower motor control circuit at the blower motor relay for an open or high resistance. Did you find and correct the condition? If so, go to step  24. If not, go to step  14.
  9. Test the blower motor relay ground circuit for an open or high resistance. Did you find and correct the condition? If so, go to step  24. If not, go to step  15.
  10. Turn the ignition off. Disconnect the blower motor relay. Turn the ignition on, with the engine off. Using a test light connected to ground, check the voltage circuit between the blower motor relay and the blower motor resistor. Place the blower motor switch in the minimum, medium (1), and medium (2) speed positions. Does the test light illuminate in each speed position? If so, go to step  15. If not, go to next step.
  11. Check the supply voltage circuit between the blower motor resistor and blower motor relay for an open, short to ground, or high resistance. Did you find and correct the condition? If so, go to step  24. If not, go to next step.
  12. Turn the ignition off. Disconnect the blower motor resistor. Turn the ignition on, with the engine off. Place the mode control in the VENT position. Probe the low, medium (1), and medium (2) blower motor control circuits with a test light that is connected to ground. Place the blower motor switch in the appropriate speed position for the circuit being tested. When the blower motor switch in is each position, does the test light illuminate? If so, go to step  17. If not go to next step.
  13. Test the suspect blower motor control circuit of the blower motor resistor for an open or high resistance. Did you find and correct the condition? If so, go to step  24. If not, go to step  18.
  14. Test the low blower motor control circuit between the HVAC control assembly and splice (S215) for an open or high resistance. Did you find and correct the condition? If so, go to step  24. If not, go to step  18.
  15. Inspect the blower motor relay for poor connections. Did you find and correct the condition? If so, go to step  24. If not, go to step  20.
  16. Inspect the blower motor for poor connections. Did you find and correct the condition? If so, go to step  24. If not, go to step  21.
  17. Inspect the blower motor resistor for poor connections. Did you find and correct the condition? If so, go to step  24. If not, go to step  22.
  18. Inspect the HVAC control assembly for poor connections. Did you find and correct the condition? If so, go to step  24. If not, go to step  23.
  19. Repair the battery voltage circuit of the blower motor relay. After repairs, go to step  24.
  20. Replace the blower motor relay. See BLOWER MOTOR RELAY  under REMOVAL & INSTALLATION. After repairs, go to step  24.
  21. Replace the blower motor. See BLOWER MOTOR & FAN  under REMOVAL & INSTALLATION. After repairs, go to step  24.
  22. Replace the blower motor resistor. See BLOWER MOTOR RESISTOR  under REMOVAL & INSTALLATION. After repairs, go to step  24.
  23. Replace the HVAC control assembly. See HVAC CONTROL ASSEMBLY  under REMOVAL & INSTALLATION. After repairs, go to step  24.
  24. Operate the system in order to verify the repair. Did you correct the condition? If so, system is okay. If not, go to step  3.
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