Four Seasons 74805 HVAC Heater Control Valve

Vacuum Heater Control Valve for OE Replacement

The Four Seasons 74805 is a vacuum open, non-bypass HVAC heater control valve built as an OE replacement for vehicles that use vacuum-operated coolant flow control. It features a plastic body with three hose connectors and is sized for common 5/8 in. and 3/4 in. heater hose connections.

For Buick Roadmaster, Chevrolet Caprice, Camaro, Commercial Chassis, Cadillac Brougham, Pontiac Firebird, and Pontiac Bonneville applications, this heater valve helps restore proper heater core coolant routing when the original valve is worn, leaking, or no longer responding to vacuum control. Four Seasons Heater Valve 74805 is a direct-fit service part for select factory air conditioning systems.

Key Features

• Vacuum open operation for vacuum-controlled HVAC systems
• Non-bypass style for direct coolant flow control through the heater circuit
• Three hose connectors for the listed OE-style plumbing layout
• Plastic construction for lightweight service replacement
• OE replacement design for select Buick, Chevrolet, Cadillac, and Pontiac vehicles
• Opening sizes: 0.625 in. (15.875 mm) and 0.750 in. (19.050 mm)

Product Details

Four Seasons Heater Valve 74805 is a vacuum-operated HVAC heater control valve used to regulate coolant flow to the heater core. The non-bypass design routes coolant through the heater circuit as specified by the vehicle’s HVAC system, while the vacuum-open function responds to engine vacuum for temperature control. This part cross-references UAC HV2004C for the same application.

Use Four Seasons 74805 when servicing heater control systems on 1987-1996 Chevrolet Camaro, 1987-1992 Pontiac Firebird, 1989-1991 Chevrolet Caprice, 1990-1991 Pontiac Bonneville, 1991-1992 Buick Roadmaster, 1991-1992 Cadillac Brougham, and related Commercial Chassis applications listed below.

What It Helps Fix

• Heater output stuck on hot or cold
• Coolant leakage at the heater valve body
• Vacuum-related loss of heater temperature control
• Restricted coolant flow to the heater core
• HVAC temperature inconsistency in vacuum-controlled systems

Installation Notes

• Verify hose connector count and hose diameters before installation.
• Confirm the vehicle uses a vacuum-open, non-bypass heater valve.
• Inspect vacuum supply lines and heater hoses for cracks or swelling before replacing the valve.
• Match the OE routing and connector orientation to the original part.
• Fits 1994-1996 Buick Roadmaster, N/A; 1991-1992 Buick Roadmaster, N/A; 1992-1996 Chevrolet Caprice, N/A; 1993-1995 Chevrolet Camaro, N/A; 1987 Chevrolet Camaro, N/A; 1992-1994 Chevrolet Commercial Chassis, N/A; 1991-1992 Cadillac Brougham, N/A; 1992 Cadillac Commercial Chassis, N/A; 1988-1992 Chevrolet Camaro, N/A; 1987-1992 Pontiac Firebird, N/A; 1989-1991 Chevrolet Caprice, N/A; 1991 Chevrolet Commercial Chassis, N/A; 1990-1991 Pontiac Bonneville, N/A; 1990 Cadillac Brougham, N/A.

Quality Assurance

Four Seasons supplies HVAC service components with OE-style replacement specifications, and part number 74805 is built to match the listed application requirements for vacuum-operated heater control systems.