Nissens 999234 A/C Expansion Valve

Nissens A/C Expansion Valve for Mercedes-Benz SLK

The Nissens 999234 A/C expansion valve regulates refrigerant flow through the air conditioning system to help maintain proper evaporator performance. Built from aluminum and specified for R134A/R1234YF systems, it is a direct-fit HVAC flow restrictor for select Mercedes-Benz SLK models.

Key Features

• Aluminum block-style A/C expansion valve
• Designed for R134A and R1234YF refrigerant systems
• Includes O-rings and mounting hardware where applicable
• OE-matching pressure performance, tightness, opening, and set-point control
• Fits select 2005-2011 Mercedes-Benz SLK applications
• Part number 999234 for easy identification

Detailed Description

Nissens part number 999234 is a thermal expansion valve engineered for precise refrigerant metering in the HVAC system. This block-type valve is used in select Mercedes-Benz SLK300, SLK350, SLK55 AMG, and SLK280 models, with fitment details that include inlet and outlet dimensions for accurate matching during service. The valve is manufactured to strict validation standards to control pressure performance, sealing integrity, opening behavior, set-point accuracy, and internal finish. If you are replacing a Mercedes-Benz SLK A/C expansion valve, 999234 provides the correct OE-style service part for the listed applications.

This part cross-references Mercedes-Benz OE numbers 1698300384 and A1718300184 for the same application.

Vehicle Fitment

• Fits 2009-2011 Mercedes-Benz SLK300, N/A. Inlet 1: 33mm, Inlet 2: 25 mm, Outlet 1: 11.8 mm, Outlet 2: 18 mm.
• Fits 2005-2011 Mercedes-Benz SLK350, N/A. Inlet 1: 33mm, Inlet 2: 25 mm, Outlet 1: 11.8 mm, Outlet 2: 18 mm.
• Fits 2005-2010 Mercedes-Benz SLK55 AMG, N/A. Inlet 1: 33mm, Inlet 2: 25 mm, Outlet 1: 11.8 mm, Outlet 2: 18 mm.
• Fits 2006-2008 Mercedes-Benz SLK280, N/A. Inlet 1: 33mm, Inlet 2: 25 mm, Outlet 1: 11.8 mm, Outlet 2: 18 mm.

Common Replacement Symptoms

• Weak or inconsistent cabin cooling
• Incorrect refrigerant metering at the evaporator
• Uneven A/C outlet temperatures
• System performance issues after A/C service
• Leak-related loss of refrigerant at the valve area

Installation Notes and Tips

Verify the inlet and outlet dimensions before installation and confirm refrigerant system compatibility with R134A or R1234YF as specified for the vehicle. Replace the O-rings during service, inspect the mating surfaces for damage, and follow the vehicle manufacturer’s evacuation and recharge procedures after installation. The part number 999234 should be matched to the exact Mercedes-Benz SLK application listed above.

Quality Assurance

Nissens manufactures this expansion valve to OE-matching standards and validates pressure performance, sealing, opening characteristics, set-point calibration, and internal finish for controlled HVAC operation.