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 CONTROLSTEMPERATURE CONTROL
1999 Chevrolet Express 1/2 Ton Van V6-4.3L VIN W
Temperature Control
1999 Chevrolet Express 1/2 Ton Van V6-4.3L VIN WSECTION Temperature Control
When the temperature knob is in the COLD (blue) position, the air delivered by the HVAC system is unheated. When the temperature knob in the HOT (red) position, all of the air that passes through the heater module is heated before the air is discharged. Intermediate positions of the temperature knob result in a mixture of heated and unheated air in order to provide more moderate air temperatures.
When you move the temperature knob away from the cold position, the temperature valve moves away from the heater core in order to allow for some air flow through the heater core. The more you move the temperature knob toward the hot position, the greater the air flow through the heater core. Heating a greater portion of the airflow in this manner results in a warmer discharge of air from the outlets.
When the temperature knob is in the full hot position, the temperature valve blocks off the passage that allows air to bypass the heater core. This causes all of the airflow to go through the heater core for maximum heating. This method of temperature control provides a very rapid response to any change in temperature selection throughout the entire range when the engine is warmed up.
An electric motor, not a cable system, controls the temperature door.
When you move the temperature knob away from the cold position, the temperature valve moves away from the heater core in order to allow for some air flow through the heater core. The more you move the temperature knob toward the hot position, the greater the air flow through the heater core. Heating a greater portion of the airflow in this manner results in a warmer discharge of air from the outlets.
When the temperature knob is in the full hot position, the temperature valve blocks off the passage that allows air to bypass the heater core. This causes all of the airflow to go through the heater core for maximum heating. This method of temperature control provides a very rapid response to any change in temperature selection throughout the entire range when the engine is warmed up.
An electric motor, not a cable system, controls the temperature door.
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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.