Nissens 999377 A/C Expansion Valve

Nissens A/C Expansion Valve for Audi HVAC Service

The Nissens 999377 A/C expansion valve is a block-style HVAC flow restrictor built from aluminum for R134A air conditioning systems. It is specified for a wide range of Audi models, including Audi A4, A5, Q5, S4, S5, RS5, RS6, RS7, SQ5, and e-tron applications with matching cooling circuit requirements.

Part number 999377 is designed for direct replacement service where precise refrigerant metering and stable A/C performance are needed. This valve includes mounting hardware and O-rings, helping support a complete repair on the vehicle’s HVAC system.

Key Features

• Aluminum block-style A/C expansion valve
• Built for R134A refrigerant systems
• Liquid inlet and outlet fitting thread diameter: 0.4700
• Suction inlet and outlet fitting thread diameter: 0.7100
• Includes O-rings and mounting hardware
• OE-style replacement for select Audi HVAC systems

Detailed Description

Nissens 999377 is an A/C expansion valve used to regulate refrigerant flow into the evaporator, helping the HVAC system maintain proper cooling performance. Nissens develops thermal management components to high manufacturing standards, and this part reflects that approach with an aluminum construction and application-specific fitment for many Audi platforms. It cross-references Audi OE part number 8W0820679 for the same application.

Compatible With Audi A4, A5, Q5, S4, S5, RS5, RS6, RS7, SQ5, and e-tron models across 2017-2025 depending on the exact vehicle and refrigerant setup. Part number 999377 is a practical choice for Audi HVAC repair when the original expansion valve is worn, restricted, or no longer controlling refrigerant flow correctly.

What This Part Helps Address

• Weak or inconsistent cabin cooling
• Refrigerant flow restriction in the A/C circuit
• Incorrect evaporator feed from a failing expansion valve
• HVAC performance issues on R134A-equipped Audi systems
• Service replacement for a leaking or degraded valve assembly

Installation Notes and Tips

Verify the vehicle’s refrigerant type and compare the inlet and outlet dimensions before installation. This valve is listed for specific Audi applications with R134A systems, and some fitments note exact inlet and outlet measurements that should be matched during service. Replace the O-rings during installation and inspect the surrounding A/C components for contamination, leaks, or blockage before recharging the system.

Quality Assurance

Nissens is a market-leading manufacturer of thermal and engine efficiency components, and its products are developed and manufactured to consistent quality standards. The brand positions this part within its Genuine Nissens Quality range for aftermarket HVAC service.