Four Seasons 74797 HVAC Heater Control Valve - Front

Four Seasons 74797 Heater Valve Overview

Four Seasons 74797 is an OE replacement HVAC heater control valve built for vacuum-operated heater circuits. It uses a bypass style design with a vacuum-closing function to regulate coolant flow through the heater system, helping maintain consistent cabin temperature control in supported Chevrolet and GMC applications.

Four Seasons Heater Valve parts are built for direct-fit service in temperature control systems, and this 74797 valve follows the original equipment style used on select GM vans and trucks. It is a practical replacement for a worn or leaking heater valve on vehicles such as the Chevrolet G30, Chevrolet P30, and GMC Savana 3500.

Key Features

• Part number 74797
• HVAC heater control valve for temperature control systems
• Vacuum-operated, vacuum closes bypass heater valve
• Bypass style with 4 hose connectors
• Plastic construction
• OE replacement design
• Opening sizes: 0.750 in (19.050 mm), 0.625 in (15.875 mm), and 0.625 in (15.875 mm)

Detailed Description

This Four Seasons heater valve is designed for vacuum-controlled coolant routing in the heater circuit. The bypass configuration helps direct coolant flow as the HVAC system commands heat, making it a direct replacement choice for vehicles that use a vacuum closes bypass heater valve. It is listed for a wide range of 1988-1996 Chevrolet and GMC applications, including front-position and non-position-specific installations on select G-series, P-series, Express, and Savana models. If you are replacing a failing heater valve on a Chevrolet G20 or GMC G2500, Four Seasons 74797 provides the correct OE-style fitment for the specified applications.

This part cross-references Carlson 15222 and SKF 25140 for the same application.

What It Helps Address

• Loss of heat due to a valve that no longer opens or closes correctly
• Coolant bypass issues in the heater circuit
• Vacuum control problems affecting heater operation
• Coolant leakage from a deteriorated heater valve body
• Inconsistent cabin temperature control in supported GM vehicles

Installation Notes and Tips

• Verify hose connector count and opening sizes before installation.
• Confirm vacuum operation matches the original valve style.
• Match the vehicle notes carefully, especially w/o Recreational Package and w/ AC applications.
• Use the listed fitment exactly for Chevrolet and GMC G-series, P-series, Express, and Savana models.
• Inspect heater hoses and vacuum lines during replacement to avoid repeat service.

Quality Assurance

Four Seasons 74797 is an OE replacement heater valve built to match the specified factory-style application requirements for compatible Chevrolet and GMC vehicles.