Four Seasons 74802 HVAC Heater Control Valve

Four Seasons 74802 Heater Valve Overview

Four Seasons 74802 is an OE replacement HVAC heater control valve built for vacuum-operated temperature control systems. It uses a non-bypass design with two hose connectors and a 0.625 in. (15.875 mm) opening, making it a direct-fit service part for restoring coolant flow control in the heater circuit.

Compatible With 1985-1988 Cadillac and Chevrolet applications, including Cadillac Commercial Chassis, Cadillac DeVille, Cadillac Fleetwood, and Chevrolet Caprice. This Four Seasons heater valve is built with thermoplastic and steel construction for HVAC service use.

Key Features

• Part number 74802 heater valve for HVAC temperature control service
• Vacuum-operated, non-bypass design
• Two hose connectors for standard heater hose routing
• 0.625 in. / 15.875 mm opening size
• Thermoplastic and steel construction
• OE replacement configuration

Product Details

Four Seasons Heater Valve line components are designed for vehicle heating systems that regulate coolant flow through the heater core. Part number 74802 uses vacuum operation to close the valve, helping restore proper cabin heat control when the original valve is worn, leaking, or no longer responding to HVAC commands. This part cross-references Unity Automotive 15161 for the same application.

Vehicle coverage includes Fits 1985-1987 Cadillac Commercial Chassis, N/A; Fits 1985-1987 Cadillac DeVille, N/A; Fits 1986-1987 Cadillac Fleetwood, N/A; Fits 1985 Cadillac Fleetwood, N/A; and Fits 1986-1988 Chevrolet Caprice, N/A, with a note that the Caprice application lists an ATC relay connector incompatibility with the HVAC blower motor resistor harness.

Common Issues This Part Can Address

• Heater core coolant flow that stays open when the HVAC system calls for heat shutoff
• Loss of cabin temperature control caused by a failed vacuum heater valve
• Coolant leakage at the heater valve body or hose connections
• Sticking or non-responsive heater control valve operation
• Improper heater performance in Cadillac and Chevrolet HVAC systems

Installation Notes

Verify hose routing, vacuum supply, and connector orientation before installation. Confirm the 0.625 in. opening size and the non-bypass layout match the original valve on the vehicle. On 1986-1988 Chevrolet Caprice applications, review the ATC relay connector note before service to avoid HVAC harness mismatch.

Quality Assurance

Four Seasons 74802 is an OE replacement heater valve built for HVAC service applications and constructed from thermoplastic and steel for durability in the cooling and heating circuit.