Nissens 999390 A/C Expansion Valve

Nissens A/C Expansion Valve for Mercedes-Benz

The Nissens 999390 A/C expansion valve helps regulate refrigerant flow in the air conditioning system for select Mercedes-Benz models. Built from aluminum and specified for R134A systems, it supports stable evaporator performance and consistent cabin cooling.

Compatible With Mercedes-Benz C300, E350, GLC300, GLC43 AMG, and related applications, this block-style valve is a direct-fit service part for vehicles using the listed inlet and outlet dimensions. Part number 999390 is also referenced for OE-style replacement needs in the same application range.

Key Features

• Aluminum construction for A/C system service durability
• Block-style A/C expansion valve design
• Specified for R134A refrigerant systems
• Mounting hardware included
• O-rings included; 4 O-rings total
• Liquid and suction fitting thread dimensions listed for application matching
• Cross-reference part numbers: 0998300100, A0998300100

Detailed Description

Nissens 999390 is an A/C expansion valve used to meter refrigerant into the evaporator based on system demand. By controlling refrigerant flow, it helps maintain proper pressure balance and cooling performance in Mercedes-Benz HVAC systems. This part number 999390 is listed for 2018-2022 Mercedes-Benz applications, including C300, E350, GLC300, GLC43 AMG, C43 AMG, C63 AMG, C63 AMG S, E63 AMG S, GLC63 AMG, GLC63 AMG S, CLS450, CLS53 AMG, E450, E53 AMG, GLC350e, and E300.

Nissens develops thermal management components with a focus on aftermarket fit and manufacturing consistency. For Mercedes-Benz C300 and GLC300 service work, as well as E350 and GLC43 AMG HVAC repairs, this valve provides the specified block configuration and refrigerant compatibility needed for proper system operation.

What It Helps Address

• Weak or inconsistent cabin cooling
• Incorrect refrigerant metering at the evaporator
• A/C performance issues caused by a worn expansion valve
• Pressure imbalance in the HVAC circuit
• Service replacement for leaking or restricted valve assemblies

Installation Notes and Tips

Verify the inlet and outlet dimensions against the original part before installation. Confirm the vehicle uses R134A refrigerant and match the block-style configuration to the existing HVAC layout. Replace the included O-rings during service and inspect the surrounding A/C components for contamination or restriction before reassembly. For 2022 Mercedes-Benz C300, E350, GLC300, and GLC43 AMG applications, confirm the listed inlet and outlet measurements: Inlet 1 35.5 mm, Inlet 2 30 mm, Outlet 1 11.8 mm, and Outlet 2 17.7 mm.

Quality Assurance

Nissens positions this part within its Genuine Nissens Quality standard, with products developed and manufactured to consistent quality requirements for aftermarket thermal management service.