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 MANUALSCHEVROLET1998EXPRESS 1 TON VAN V8-5.7L VIN RREPAIR AND DIAGNOSISHEATING AND AIR CONDITIONINGCONTROL ASSEMBLYDESCRIPTION AND OPERATION
1998 Chevrolet Express 1 Ton Van V8-5.7L VIN R
Control Assembly: Description and Operation
1998 Chevrolet Express 1 Ton Van V8-5.7L VIN RSECTION Description and Operation
The temperature of the air coming from the heater duct and defroster nozzle is regulated by controlling the relative amounts of warm and cool air coming from the heater module. The amount of the total airflow that is allowed to pass through the heater core is governed by the temperature valve.
When the temperature knob in the control assembly is in the extreme left side of its travel, in the full "BLUE" (Cold) position, the temperature valve is positioned to stop all of the airflow through the heater core so only unheated air is sent to the heater duct and defroster nozzle.
As the temperature knob is moved away from the full "BLUE" (Cold) position, the temperature valve opens to allow an increasing amount of air to pass through the heater core. At the same time, the temperature valve reduces the amount of unheated air that is allowed to enter the mixture. This results in a very responsive control of the temperature of the air discharged through the heater ducts and defroster nozzle.
When the temperature knob reaches the full "RED" (Hot) position to the extreme right end of its travel, the temperature valve in a position that diverts all of the airflow through the heater core for maximum heating.
Hot coolant from the engine is directed through the heater core and returned to the cooling system when the engine is running.
When the temperature knob in the control assembly is in the extreme left side of its travel, in the full "BLUE" (Cold) position, the temperature valve is positioned to stop all of the airflow through the heater core so only unheated air is sent to the heater duct and defroster nozzle.
As the temperature knob is moved away from the full "BLUE" (Cold) position, the temperature valve opens to allow an increasing amount of air to pass through the heater core. At the same time, the temperature valve reduces the amount of unheated air that is allowed to enter the mixture. This results in a very responsive control of the temperature of the air discharged through the heater ducts and defroster nozzle.
When the temperature knob reaches the full "RED" (Hot) position to the extreme right end of its travel, the temperature valve in a position that diverts all of the airflow through the heater core for maximum heating.
Hot coolant from the engine is directed through the heater core and returned to the cooling system when the engine is running.
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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.