Four Seasons 74610 HVAC Heater Control Valve

Vacuum Heater Control Valve for OE Replacement

The Four Seasons 74610 is a vacuum-operated heater control valve built as an OE replacement for temperature control systems that use a non-bypass design. It uses a steel body, two hose connectors, and a 0.625 in. (15.875 mm) opening to regulate coolant flow through the heater circuit.

For classic Chevrolet Corvette, Camaro, Impala, and Nova applications, as well as select Cadillac and GMC models, this Four Seasons Heater Valve line part helps restore proper heater control when the original valve no longer opens and closes correctly. Part number 74610 is also cross-referenced as Hayden 5900 for the same application.

Key Features

• Vacuum closes non-bypass heater valve
• Steel construction for heater circuit service
• Two hose connectors
• 0.625 in. / 15.875 mm opening
• OE replacement design
• Non-bypass style
• Vacuum operation type

Product Details

Four Seasons 74610 is part of the Heater Valve product line and is engineered for HVAC temperature control systems that route coolant through a vacuum-actuated heater valve. The non-bypass configuration means coolant flow is controlled through the valve rather than routed around it, which is important for vehicles that rely on this style of heater circuit. This part number appears in interchange listings for several aftermarket and OE-reference applications, including 74610 and 20103.

Fits 1969-1970 Chevrolet Camaro, Compatible with vehicles equipped with air conditioning; Heater Valve. Fits 1969-1970 Chevrolet Caprice, Compatible with vehicles equipped with air conditioning; Heater Valve. Fits 1969-1970 Chevrolet Impala, Compatible with vehicles equipped with air conditioning; Heater Valve. Fits 1970 Chevrolet Monte Carlo, Heater Valve. Fits 1969-1970 Chevrolet Nova, Heater Valve. Fits 1979-1981 Chevrolet Corvette, Heater Valve. Fits 1977-1979 Cadillac Seville, Heater Valve. Fits 1977-1978 Cadillac Eldorado, Heater Valve. Fits 1979 Cadillac Eldorado, Curved; Heater Valve.

Common Repair Uses

• Restores heater coolant shutoff when the original valve sticks open
• Addresses weak or inconsistent cabin heat control
• Helps correct coolant flow issues in vacuum-controlled HVAC systems
• Replaces a leaking or corroded heater valve body
• Supports repair of classic GM heater circuit service problems

Installation Notes and Tips

Verify the vehicle uses a vacuum-operated, non-bypass heater valve before installation. Match the 0.625 in. hose opening and confirm the hose routing and valve orientation against the original part. Mounting hardware is not included, so reuse or source the correct hardware as needed. Because fitment varies by model and equipment, confirm the application details for Chevrolet Corvette, Camaro, Impala, Nova, and other listed vehicles before service.

Quality Assurance

Four Seasons supplies HVAC temperature control components for OE-style replacement service. Part number 74610 is built to match the listed application requirements and interchange references for direct replacement use.