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HOMESERVICE MANUALSGMC1999FORWARD CONTROL 5.7 R, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 30 (HVAC SYSTEMS - AUTOMATIC)SYMPTOM TESTSTEST E: BLOWER MOTOR DOES NOT OPERATE IN ANY MODE
1999 GMC Forward Control 5.7 R, Automatic

Test E: Blower Motor Does Not Operate In Any Mode

1999 GMC Forward Control 5.7 R, AutomaticSECTION Test E: Blower Motor Does Not Operate In Any Mode
WARNING: This page is about a different car, the 2002 Oldsmobile Aurora. However, it is still accessible from the selected car via links, so may be relevant.
  1. Perform diagnostic system check. See DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. After performing system check, go to next step.
  2. Turn ignition on, engine off. Turn blower switch to each blower position. If blower motor operates in any of the switch positions, check for loose wires and/or connectors to blower switch harness connector. If blower motor does not operate in any of the blower speed switch positions, go to next step.
  3. Connect scan tool. Place Blower Motor in maximum speed position. Observe COMMAND BLOWER parameter in INSTRUMENT PANEL MODULE data list. If scan tool indicates COMMAND parameter is near 100 percent, go to step  5. If scan tool indicates COMMAND BLOWER parameter is not near 100 percent, go to next step.
  4. Use scan tool to command BLOWER MOTOR ON, observe scan tool COMMANDED BLOWER parameter in INSTRUMENT PANEL MODULE data list. If scan tool indicates COMMAND BLOWER parameter is near 100 percent, go to step  15. If scan tool indicates COMMAND BLOWER parameter is not near 100 percent, go to step  16.
  5. Turn ignition off. Disconnect Blower Motor harness connector. Turn ignition ON, engine OFF. Connect a test light between terminal "B" (Purple wire) and terminal "A" of Blower Motor harness connector. Switch blower motor to minimum speed position. If test light illuminates, go to step  11. If test light does not illuminate, go to next step.
  6. Check Orange wire between Blower Motor control processor terminal B and HVAC fuse block terminal A1 for open, high resistance or short to ground. If problem is found, repair as necessary. Go to step  21. If problem is not found, go to next step.
  7. Check Black wire between terminal "A" of Blower Motor harness connector and Blower Motor Control harness connector for open, high resistance. See Fig 1. If problem is found, repair as necessary. Go to step  21. If problem is not found, go to next step.
    8. NOTE: Ensure Blower Motor Control Processor and IPM connectors are connected before proceeding.
  8. Measure voltage between ground and terminal D11 (Gray/Black wire). Connect scan tool. Command Blower Motor ON and OFF. If voltage is 5 volts with Blower Motor OFF and 1.5 volts with Blower Motor ON, go to step  12. If voltage is not 5 volts with blower motor OFF and 1.5 volts with blower motor ON, go to next step.
  9. Turn ignition off. Disconnect IPM harness connector C1. Turn ignition on, engine off. Measure voltage between ground and terminal D11 (Gray/Black wire) of IPM harness connector C1. See Figure. If 5 volts exists, go to next step. If 5 volts does not exist, go to step  16
  10. Check (Gray/Black wire) of IPM harness connector between terminal D11 and Blower Motor Control Processor terminal C for an open, short to ground or short to voltage. If problem is found, repair as necessary. Go to step  21. If problem is not found, go to step  14.
  11. Check for loose wires and connectors at Blower Motor harness connector. If poor connection is found, repair as necessary. Go to step  21. If poor connection is not found, go to step  17.
  12. Check (Black wire) between blower motor terminal "A" and Blower Motor Control Processor for an open, or high resistance. See Fig 1. If problem is found, repair as necessary. Go to step  21. If problem is not found, go to next step.
  13. Check (Purple wire) between Blower Motor terminal B and blower motor control processor for an open, or high resistance. See Fig 1. If problem is found, repair as necessary. Go to step  21. If problem is not found, go to next step.
  14. Check for loose wires and connectors at Blower Motor Control Processor. See Fig 1. If problem is found, repair as necessary. Go to step  21. If problem is not found, go to step  18.
  15. Check for loose wires and connectors at HVAC Control Module harness connector. If problem is found, repair as necessary. Go to step  21. If problem is not found, go to step  19.
  16. Check for loose wires and connectors at Instrument Panel Module (IPM) harness connector. If problem is found, repair as necessary. Go to step  21. If problem is not found, go to step  20.
  17. Replace Blower Motor. See BLOWER MOTOR  under REMOVAL & INSTALLATION. Go to step  21.
  18. Replace Blower Motor Control Processor. See BLOWER MOTOR CONTROL PROCESSOR  under REMOVAL & INSTALLATION. Go to step  21.
  19. Replace HVAC Control Module. See HVAC CONTROL MODULE  under REMOVAL & INSTALLATION. Go to step  21.
  20. Replace IPM. See INSTRUMENT PANEL MODULE (IPM)  under REMOVAL & INSTALLATION.
  21. Operate system to verify repair. If condition is corrected, system is okay. If condition is not corrected, go to step  2.
Fig 1: Identifying Blower Motor Control Processor Connector Terminals
G00056192Courtesy of GENERAL MOTORS CORP.
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