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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 Temperature Actuator Inoperative

Auxiliary Temperature Actuator Inoperative

  1. Perform AIR DELIVERY SYSTEM CHECK . Go to next step.
  2. Turn ignition switch to ON position. With a DVOM negative lead connected to ground, backprobe for voltage at auxiliary HVAC logic module connector terminal "B" (Dark Blue wire). See WIRING DIAGRAMS . Monitor DVOM while adjusting front and rear auxiliary temperature controls from hot to cold. If voltage reading varies smoothly, go to next step. If voltage reading is erratic and does not vary smoothly, go to step  10.
  3. Turn ignition switch to OFF position. Disconnect auxiliary HVAC logic module connector. Disconnect auxiliary temperature door actuator connector. Use a DVOM to check for continuity between auxiliary HVAC logic module connector terminal "B" and auxiliary temperature door actuator connector terminal No. 8 (Dark Blue wire). If continuity is indicated, go to step  5. If continuity is not indicated, go to next step.
  4. Repair open in Dark Blue wire between auxiliary HVAC logic module and auxiliary temperature door actuator. Go to AIR DELIVERY SYSTEM CHECK .
  5. Use a DVOM to check continuity between ground and auxiliary temperature 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 temperature door actuator and 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 temperature 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 temperature door actuator and splice S400. Splice S400 is located approximately 6.5" (17 cm) from auxiliary blower relays breakout, toward blower motor. Go to AIR DELIVERY SYSTEM CHECK .
  9. Replace auxiliary temperature door actuator. 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 battery voltage is indicated, go to step  12. If battery 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 "A" (Light Blue wire). Monitor DVOM while rotating front auxiliary A/C-heater control assembly temperature control from hot to cold position. Use a DVOM to measure voltage between ground and auxiliary HVAC logic module connector terminal "C" (Dark Blue wire). Monitor DVOM while rotating rear auxiliary A/C-heater control assembly temperature control from hot to cold position. 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.
  14. If terminal "A" (Light Blue wire) from front auxiliary A/C-heater control assembly, terminal "C" (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 "H" (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 step  16. If voltage reading is erratic and does not vary smoothly, go to next step.
  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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