Four Seasons 74602 HVAC Heater Control Valve

Four Seasons 74602 Heater Valve Overview

The Four Seasons Heater Valve 74602 is an OE replacement HVAC heater control valve built for vacuum-operated heating systems. It uses a non-bypass, vacuum-closing design with two hose connectors and steel construction for direct replacement in supported Cadillac, Buick, and Oldsmobile applications.

Four Seasons Heater Valve line components are built for temperature-control service where coolant flow must be regulated through the heater circuit. This part number, 74602, is specified for vehicles that use a vacuum-closing non-bypass valve and the listed hose opening sizes.

Key Features

• Vacuum-operated heater control valve
• Non-bypass style for direct heater circuit control
• OE replacement design
• Steel construction
• Two hose connectors
• Opening sizes: 0.625 in (15.875 mm) and 0.750 in (19.050 mm)

Detailed Description

Four Seasons 74602 is an HVAC heater control valve used to regulate coolant flow through the heater core in vacuum-controlled systems. The non-bypass configuration closes under vacuum, matching the operating style used in many classic GM applications. If you are replacing a worn heater valve on a Cadillac Brougham, Buick Riviera, or Oldsmobile 98, this OE-style part number 74602 provides the correct valve format for the listed fitments.

This part cross-references Hayden 5902 for the same application. It also aligns with other listed interchange numbers for service matching, including Four Seasons 20124.

Vehicle Fitment

• Fits 1990 Cadillac Brougham, N/A — 2 Ports w/ Horizonal Water Outlet; Heater Valve
• Fits 1988-1989 Cadillac Brougham, N/A — w/ Vertical Water Outlet; Heater Valve
• Fits 1988-1989 Cadillac Fleetwood, N/A — w/ Vertical Water Outlet; Heater Valve
• Fits 1987 Cadillac Brougham, N/A — Heater Valve
• Fits 1979-1986 Cadillac Fleetwood, N/A — Heater Valve
• Fits 1979-1985 Cadillac Eldorado, N/A — Heater Valve
• Fits 1979-1985 Cadillac Seville, N/A — Heater Valve
• Fits 1979-1984 Cadillac DeVille, N/A — Heater Valve
• Fits 1980 Buick LeSabre, N/A — Fits straight hose for HVAC Heater Control Valve; Heater Valve
• Fits 1980 Buick Riviera, N/A — Fits straight hose for HVAC Heater Control Valve; Heater Valve
• Fits 1980 Buick Riviera, N/A — w/ ECC; Heater Valve
• Fits 1977-1979 Buick Century, N/A — Straight hose connection with threads; Heater Valve
• Fits 1977-1979 Buick LeSabre, N/A — Straight hose connection with threads; Heater Valve
• Fits 1979 Buick Riviera, N/A — Right Angle Hose Connection; Straight Hose Connection; w/ Threads; Heater Valve
• Fits 1978-1979 Oldsmobile 98, N/A — Fits HVAC Heater Control Valve.; Heater Valve
• Fits 1979 Oldsmobile Custom Cruiser, N/A — Fits HVAC Heater Control Valve.; Heater Valve
• Fits 1979 Oldsmobile Delta 88, N/A — Fits HVAC Heater Control Valve.; Heater Valve
• Fits 1979 Oldsmobile Toronado, N/A — Fits HVAC Heater Control Valve.; Heater Valve
• Fits 1977-1978 Buick Riviera, N/A — Straight hose connection with threads; Heater Valve
• Fits 1977 Buick Regal, N/A — Straight hose connection with threads; Heater Valve
• Fits 1971-1976 Oldsmobile 98, N/A — Heater Valve
• Fits 1976 Oldsmobile Toronado, N/A — Fitment note: with 5/8" x 3/4" NPT x 5/16" NF Thread.; Heater Valve
• Fits 1971-1975 Oldsmobile Custom Cruiser, N/A — Heater Valve
• Fits 1971-1975 Oldsmobile Cutlass, N/A — Heater Valve
• Fits 1975 Oldsmobile Cutlass Salon, N/A — Heater Valve
• Fits 1971-1975 Oldsmobile Cutlass Supreme, N/A — Heater Valve
• Fits 1971-1975 Oldsmobile Delta 88, N/A — Heater Valve
• Fits 1971-1975 Oldsmobile Toronado, N/A — Heater Valve
• Fits 1973-1974 Oldsmobile Omega, N/A — Fitment note: with 5/8" x 3/4" NPT x 5/16" NF Thread.; Heater Valve

Common Repair Uses

• Restores heater coolant flow control when the original valve sticks open or closed
• Addresses weak cabin heat caused by a leaking or restricted heater valve
• Replaces a vacuum heater valve that no longer responds to HVAC control input
• Helps correct coolant seepage at the heater hose connection points
• Supports proper temperature regulation in classic Cadillac, Buick, and Oldsmobile HVAC systems

Installation Notes and Tips

Verify the valve style, hose opening sizes, and vacuum operation before installation. This part is a non-bypass heater valve, so it should be matched to the vehicle’s original HVAC routing and hose configuration. Confirm whether the application uses a straight hose, right-angle hose, or threaded connection as noted in the fitment data, especially on Buick Riviera and Oldsmobile Toronado applications.

Inspect the heater hoses, clamps, and vacuum supply line during replacement to avoid repeat failures. For best results, compare the removed valve to the new Four Seasons 74602 before final assembly.

Quality Assurance

Four Seasons supplies this heater valve as an OE replacement part for temperature-control service. The steel construction and application-specific vacuum operation support accurate fitment in the listed vehicles, including Cadillac Brougham, Buick Riviera, and Oldsmobile 98 applications.