Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSGMC1999FORWARD CONTROL 5.7 R, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 599 (HEATING, VENTILATION AND AIR CONDITIONING)
1999 GMC Forward Control 5.7 R, Automatic
Section 599 (Heating, Ventilation And Air Conditioning)
1999 GMC Forward Control 5.7 R, AutomaticSECTION Section 599 (Heating, Ventilation And Air Conditioning)
WARNING: This page is about a different car, the 2004 Pontiac Aztek and 2004 Buick Rendezvous. However, it is still accessible from the selected car via links, so may be relevant.
- Specifications
- Diagnostic Information and Procedures
- Diagnostic Starting Point - Heating, Ventilation and Air Conditioning
- Leak Testing
- Air Conditioning (A/C) System Performance Test
- Air Conditioning (A/C) Diagnostics - Pressure Zone A
- Air Conditioning (A/C) Diagnostics - Pressure Zone B
- Air Conditioning (A/C) Diagnostics - Pressure Zone C
- Air Conditioning (A/C) Diagnostics - Pressure Zone D
- Heating Performance Diagnostic
- Defrosting Insufficient
- Noise Diagnosis - Blower Motor
- Noise Diagnosis - Air Conditioning (A/C) System
- Noise Diagnosis - HVAC Module
- Odor Diagnosis
- Repair Instructions
- Odor Correction
- Refrigerant Recovery and Recharging
- Flushing
- Compressor Oil Balancing
- Compressor Replacement
- Compressor Pressure Relief Valve Replacement
- Sealing Washer Replacement
- O-Ring Replacement
- Discharge Hose Replacement (LA1)
- Discharge Hose Replacement (LY7)
- Suction Hose Replacement (LA1)
- Suction Hose Replacement (LY7)
- Evaporator Tube Replacement - Inlet (LA1)
- Evaporator Tube Replacement - Inlet (LY7)
- Evaporator Tube Replacement - Outlet (LA1)
- Evaporator Tube Replacement - Outlet (LY7)
- Compressor Relay Replacement
- Service Ports Replacement
- Receiver Dehydrator Replacement
- Thermal Expansion Valve Replacement
- Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement
- Evaporator Temperature Sensor Replacement
- Condenser Replacement
- HVAC Module Assembly Replacement
- Evaporator Core Replacement
- Heater Hose Replacement - Inlet (LA1)
- Heater Hose Replacement - Inlet (LY7)
- Heater Pipes Replacement (LY7)
- Heater Hose Replacement - Outlet (LA1)
- Heater Hose Replacement - Outlet (LY7)
- Heater Pipe Replacement - Inlet
- Blower Motor Resistor Assembly Replacement
- Mode Linkage Adjustment
- Blower Motor Replacement
- Air Outlet Replacement - Side Window (Aztek)
- Air Outlet Replacement - Side Window (Rendezvous)
- Deflector Replacement - Instrument Panel Air (Aztek)
- Deflector Replacement - Instrument Panel Air (Rendezvous)
- Outlet Replacement - Auxiliary Air - Floor Console (Aztek)
- Outlet Replacement - Auxiliary Air - Floor Console (Rendezvous)
- Air Outlet Replacement - Floor
- Air Outlet Replacement - Center Floor
- Air Outlet Replacement - Rear Floor
- Air Outlet Duct Replacement - Defroster
- Instrument Panel (I/P) Air Outlet Ducts Replacement
- Air Outlet Replacement - Center
- Defogger Outlet Duct Replacement - Side Window (w/o UV6)
- Defogger Outlet Duct Replacement - Side Window (w/ UV6)
- Air Temperature Door Replacement
- Air Temperature Door Replacement - Right
- Air Temperature Door Replacement - Left
- Defroster Door Replacement
- Floor Air Door Replacement
- Mode Door Replacement
- Mode Door Replacement - Secondary (Single Zone)
- Mode Door Replacement - Secondary (Dual Zone)
- Defroster Door Replacement - Secondary
- Recirculation Door Replacement
- Heater Core Cover Replacement
- Heater Core Replacement (LA1)
- Heater Core Replacement (LY7)
- Special Tools and Equipment
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.