Four Seasons 74940 HVAC Heater Control Valve

Four Seasons 74940 Heater Valve Overview

Four Seasons 74940 is a rotary electronic heater valve built for HVAC temperature control in select Mercedes-Benz applications. It uses an electric bypass design with a plastic body and 4 connectors to regulate heater coolant flow for consistent cabin temperature control.

Compatible With Mercedes-Benz E320, E350, E550, E63 AMG, CLS500, CLS55 AMG, E500, and E55 AMG applications listed below, this heater control valve is a direct-fit service part for vehicles that use the specified rotary electronic valve configuration.

Key Features

• Part number: 74940
• Rotary electronic heater valve design
• Electric valve operation for HVAC temperature control
• Bypass style construction
• Plastic housing
• 4 connector electrical interface
• Opening size: 0.73 in. on B, C, and D ports; 0.78 in. opening
• Four Seasons Heater Valve product line

Product Details

The Four Seasons Heater Valve line focuses on HVAC temperature control components for mobile air conditioning and heating systems. Part number 74940 is engineered and tested for dependable operation, drawing on Four Seasons’ long history in mobile A/C and climate control parts. This valve manages coolant flow through the heater circuit, helping the HVAC system respond correctly to temperature commands in Mercedes-Benz E-Class and CLS applications.

This part cross-references Gates EHV139 for the same application.

Vehicle Fitment

• Fits 2005-2009 Mercedes-Benz E320, N/A, w/o Auxilary Unit; Heater Valve
• Fits 2006-2009 Mercedes-Benz E350, N/A, w/o Auxilary Unit; Heater Valve
• Fits 2007-2009 Mercedes-Benz E550, N/A, w/o Auxilary Unit; Heater Valve
• Fits 2007-2009 Mercedes-Benz E63 AMG, N/A, w/o Auxilary Unit; Heater Valve
• Fits 2006 Mercedes-Benz CLS500, N/A, Heater Valve
• Fits 2006 Mercedes-Benz CLS55 AMG, N/A, Heater Valve
• Fits 2003-2006 Mercedes-Benz E500, N/A, w/o Auxilary Unit; Heater Valve
• Fits 2003-2006 Mercedes-Benz E55 AMG, N/A, w/o Auxilary Unit; Heater Valve

Common Issues This Part Can Address

• Inconsistent cabin heat output
• Heater stuck on hot or cold
• Temperature changes that do not respond correctly to HVAC controls
• Coolant flow problems through the heater circuit
• Faulty heater valve operation in Mercedes-Benz climate control systems

Installation Notes and Tips

Verify the vehicle’s heater valve style, connector count, and application notes before installation. This part is listed for vehicles without the auxiliary unit where noted, so confirm the HVAC configuration on the vehicle before replacement. Compare the original valve’s connector layout and port dimensions to the replacement part to ensure proper fitment.

Quality Assurance

Four Seasons states that its HVAC and mobile A/C components are engineered and tested for years of trouble-free operation. Backed by more than 50 years of mobile A/C experience, the brand positions this heater valve line as a repair-focused replacement for dependable climate control service.