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 MANUALSPONTIAC1991FIREBIRD FORMULA, 5.0 F, STANDARD, M39REPAIR AND DIAGNOSIS (SINGLE PAGE)HEATING, VENTILATION & A/C (HVAC)HVAC CONTROL SYSTEMSHEATER SYSTEM
1991 Pontiac Firebird Formula, 5.0 F, Standard, M39
Heater System
1991 Pontiac Firebird Formula, 5.0 F, Standard, M39SECTION Heater System
- Model Identification
- Body/Model Designations
- System Description
- Vent-Heater-Defroster Lever Operation
- Temperature Lever Operation
- Fan Switch Operation
- Ventilation System Operation
- Servicing Precautions
- Air Bag System Functional Check
- Trouble Shooting
- Testing
- Blower Motor Test ("A", "F", "J" & "N" Body)
- Blower Motor Test ("L" & "W" Body)
- Heater Blower Relay Test ("L" Body)
- High Speed Blower Relay Test ("W" Body)
- Low Speed Blower Relay Test ("W" Body)
- Blower Motor Resistor Test ("A", "F", "J" & "N" Body)
- Blower Motor Resistor Test ("L" Body)
- Blower Motor Resistor Test ("W" Body)
- Blower Switch Test ("A", "F", "J" & "N" Body)
- Blower Switch Test ("L" Body)
- Blower Switch Test ("W" Body)
- Heater Control ASSY Blower Control Test ("W" Body)
- Solenoid Box Test ("W" Body)
- Heater Control Assembly Solenoid Test ("W" Body)
- Air Temp Valve Motor Test ("W" Body)
- Heater Control Panel Assembly R & I ("A" Body)
- Heater Control Panel Assembly R & I ("F" Body)
- Heater Control Panel Assembly R & I ("J" Body)
- Heater Control Panel Assembly R & I ("L" Body)
- Heater Control Panel Assembly R & I ("N" Body)
- Heater Control Panel Assembly R & I ("W" Body)
- Heater Core R & I ("A" Body)
- Heater Core R & I ("F" Body)
- Heater Core R & I ("L" Body)
- Heater Core R & I ("J", "N" Body)
- Heater Core R & I ("W" Body)
- Blower Motor R & I Except ("W" Body)
- Blower Motor R & I ("W" Body)
- Wiring Diagrams
RENDER: 1.0x
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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.