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 MANUALSCHEVROLET1999EXPRESS 1/2 TON VAN V6-4.3L VIN WREPAIR AND DIAGNOSISHEATING AND AIR CONDITIONINGCONTROL ASSEMBLYDESCRIPTION AND OPERATIONHVAC SYSTEM - MANUALMODE CONTROLSMODE CONTROL KNOB
1999 Chevrolet Express 1/2 Ton Van V6-4.3L VIN W
Mode Control Knob
1999 Chevrolet Express 1/2 Ton Van V6-4.3L VIN WSECTION Mode Control Knob
The mode knob operates a rotary vacuum that routes engine vacuum to specific hoses in the vacuum harness. These hoses control vacuum actuators on the HVAC module. Each actuator operates a valve, a door-like hinge deflector, that routes airflow to the various outlets of the heater system.
The mode knob has the following positions:
^ MAX A/C
^ NORM A/C
^ BI-LEV A/C
^ VENT
^ HTR
^ BLEND
^ DEFROST
The mode knob has the following positions:
^ MAX A/C
^ NORM A/C
^ BI-LEV A/C
^ VENT
^ HTR
^ BLEND
^ DEFROST
RENDER: 1.0x
NO RELATED
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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.