Four Seasons 74778 HVAC Heater Control Valve - Front

Four Seasons 74778 Heater Valve Overview

Four Seasons 74778 is an OE replacement HVAC heater control valve for vehicles with an auxiliary unit. This vacuum-operated, non-bypass heater valve helps regulate coolant flow through the heater circuit on compatible Chrysler, Dodge, and Plymouth applications, including Caravan, Grand Caravan, Voyager, Grand Voyager, and Town & Country models.

The Four Seasons Heater Valve line focuses on direct-fit temperature control components for automotive HVAC systems. Part number 74778 follows the original equipment style for the listed applications and uses a thermoplastic and steel construction with three hose connectors.

Key Features

• Vacuum closes non-bypass heater valve design
• OE replacement for factory-style fit and function
• Three hose connectors for the specified HVAC routing
• Bypass: Yes
• Material: thermoplastic / steel
• Opening size: 0.625 in. (15.875 mm)
• Operation type: vacuum

Detailed Product Description

Four Seasons 74778 is built as an HVAC heater control valve for temperature management in the heater circuit. It is a vacuum-operated, non-bypass style valve that closes under vacuum to control coolant flow, matching the needs of the listed auxiliary-unit applications. This part number 74778 is used on select 1984-1995 Chrysler Town & Country, 1984-1995 Dodge Caravan, 1987-1995 Dodge Grand Caravan, 1987-1995 Plymouth Grand Voyager, and 1984-1995 Plymouth Voyager models with an auxiliary unit and heater valve configuration. This part cross-references UAC HV3615 for the same application.

What It Helps Address

• Heater output that stays on when the HVAC system calls for reduced coolant flow
• Loss of cabin temperature control through the heater circuit
• Vacuum-controlled heater valve operation issues
• Coolant routing problems in auxiliary heater unit applications
• Replacement needs for a worn or leaking heater control valve

Installation Notes and Tips

Verify the vehicle’s heater hose routing, vacuum control, and auxiliary unit configuration before installation. Match the 0.625 in. openings and three-connector layout to the original valve, and confirm the non-bypass style before replacing the part. For best results, inspect adjacent hoses and vacuum lines for wear while servicing the HVAC system.

Quality Assurance

Four Seasons supplies OE replacement HVAC components for temperature control applications. Part number 74778 is built to match the listed factory-style heater valve requirements for the specified Chrysler, Dodge, and Plymouth vehicles.