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Home >> GMC >> 2000 >> C3500 HD 6.5 F, Standard >> Repair and Diagnosis >> Heating, Ventilation & A/C (HVAC) >> HVAC Control Systems >> HVAC System - Manual - Escalade, Pickup, TAHOE & YUKON >> Trouble Shooting >> Auxiliary Mode Door Actuator Inoperative

Auxiliary Mode Door Actuator Inoperative

  1. Perform AIR DELIVERY SYSTEM CHECK . Go to next step.
  2. Turn ignition switch to ON position. With DVOM negative lead connected to ground, backprobe auxiliary HVAC logic module connector terminal "F" (White wire). See WIRING DIAGRAMS . Monitor DVOM reading while rotating front and rear auxiliary mode control knobs from upper to lower outlet settings. If voltage reading varies smoothly, go to next step. If voltage reading is erratic and does not vary smoothly, go to step  10.
  3. Disconnect auxiliary HVAC logic module and auxiliary mode door actuator connectors. Use a DVOM to check for continuity of White wire between auxiliary HVAC logic module connector terminal "F" and auxiliary mode door actuator connector terminal No. 8. If continuity is indicated, go to step  5. If continuity is not indicated, go to next step.
  4. Repair open in White wire between auxiliary HVAC logic module and auxiliary mode door actuator. Go to AIR DELIVERY SYSTEM CHECK .
  5. Use a DVOM to check for continuity between ground and auxiliary mode door actuator connector terminal No. 7 (Black wire). If continuity is indicated, go to step  7. If continuity is not indicated, go to next step.
  6. Repair open in Black wire between auxiliary mode door actuator and splice S403. Splice S403 is located approximately 2.5" (7 cm) from auxiliary blower motor resistor breakout, toward blower motor. Go to AIR DELIVERY SYSTEM CHECK .
  7. Use a DVOM to measure voltage between ground and auxiliary mode door actuator connector terminal No. 10 (Brown wire). If battery voltage is indicated, go to step  9. If battery voltage is not indicated, go to next step.
  8. Repair open in Brown wire between auxiliary mode door actuator and splice S400. Splice S400 is located approximately 6.5" (17 cm) from auxiliary blower motor relays breakout toward blower motor. Go to AIR DELIVERY SYSTEM CHECK .
  9. Remove auxiliary mode door actuator and ensure that door moves freely and does not bind. If door is okay, replace auxiliary mode actuator. See ACTUATORS  under REMOVAL & INSTALLATION. Go to AIR DELIVERY SYSTEM CHECK .
  10. Disconnect auxiliary HVAC logic module connector. Use a DVOM to measure voltage between ground and auxiliary HVAC logic module connector terminal "J" (Brown wire). If voltage is indicated, go to step  12. If voltage is not indicated, go to next step.
  11. Repair open in Brown wire between auxiliary HVAC logic module and splice S308. Splice S308 is located approximately 2" (5 cm) from auxiliary blower relays breakout, toward blower motor. Go to AIR DELIVERY SYSTEM CHECK .
  12. Use a DVOM to measure voltage between ground and auxiliary HVAC logic module connector terminal "E" (Light Blue wire). Rotate front auxiliary mode control knob from upper to lower outlet settings. Measure voltage between ground and auxiliary HVAC logic module connector terminal "D" (Dark Blue wire). Monitor DVOM while rotating rear auxiliary mode control knob from upper to lower outlet settings. If voltage reading varies smoothly, go to next step. If voltage reading is erratic and does not vary smoothly, go to step  14.
  13. Replace auxiliary HVAC logic module. See AUXILIARY A/C-HEATER CONTROL ASSEMBLIES  under REMOVAL & INSTALLATION. Go to AIR DELIVERY SYSTEM CHECK .
  14. If terminal "E" (Light Blue wire) from front auxiliary A/C-heater control assembly, terminal "D" (Dark Blue wire) from rear auxiliary A/C-heater control assembly or both circuits are at fault, connect negative lead of DVOM to ground and backprobe front or rear auxiliary A/C-heater control assembly connector terminal "J" (Light Blue wire on front module; Dark Blue wire on rear module). Monitor DVOM reading while rotating front or rear auxiliary mode control knob from upper to lower outlet settings. If voltage reading varies smoothly, go to next step. If voltage reading is erratic and does not vary smoothly, go to step  16.
  15. Replace suspect auxiliary A/C-heater control assembly. See AUXILIARY A/C-HEATER CONTROL ASSEMBLIES  under REMOVAL & INSTALLATION. Go to AIR DELIVERY SYSTEM CHECK .
  16. Repair source of high resistance or short in Dark Blue wire or Light Blue wire between suspect auxiliary A/C-heater control assembly and auxiliary HVAC logic module. Go to AIR DELIVERY SYSTEM CHECK .
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