Parts for your 2008 Audi Q5-Tx valve

2008 Audi Q5 TX-valve (Expansion Valve) — Fitment, Purpose, and Service Tips

Based on Audi’s technical literature, the 2008 Audi Q5 (Type 8R) does use a TX-valve (thermostatic expansion valve, often called an H-valve). Audi ErWin/ELSA workshop information for the Q5 Heating & Air Conditioning – Refrigerant Circuit, along with the Audi ETKA parts catalogue (model 8R, groups 819/820), lists an expansion valve at the evaporator inlet, typically referenced under part number 8K0 820 179. These sources confirm the TX-valve is fitted from factory, working in tandem with the variable displacement compressor used on this platform.

On a 2008 Q5, the TX-valve meters liquid refrigerant into the evaporator and keeps superheat in the sweet spot, so cabin temps stay stable without the vents going arctic one minute and lukewarm the next. When the valve starts sticking or metering poorly, the system can feel underdone on hot days, or surge and frost up around the pipes. Because the valve reacts to evaporator temperature and pressure, it’s central to how efficiently the Q5’s climate system copes with stop–start traffic and long motorway runs alike.

When servicing, a few sensible checks go a long way:

• Tell-tale signs of a crook TX-valve: weak cooling at idle, rapid temperature swings, low-side icing, high pressure differential, or metallic debris after compressor drama.
• Replacement is straightforward for a pro: recover refrigerant (ARCtick-certified in AU/NZ), access the valve at the evaporator connections, replace O-rings, torque to spec, vacuum, and recharge with the correct R134a mass and PAG oil. Always follow the under‑bonnet label for charge volume.
• If the system’s been open to air or a compressor has let go, add a receiver–drier (integrated in the condenser on the Q5) and carry out a proper flush where recommended by the workshop manual.
• Check the cabin filter and drain for good airflow and to avoid musty odours that can mask A/C performance issues.

There’s essentially no routine “maintenance” for the TX-valve itself—think of it as a fit-and-forget component until symptoms show. That said, periodic A/C servicing every couple of years helps keep moisture out and performance up. A reputable technician will leak-test, verify pressures and temperatures, and confirm the valve is doing its job without overworking the compressor.

• Does the 2008 Audi Q5 use a TX-valve or an orifice tube?
  It uses a TX-valve (H-valve) at the evaporator. Audi’s service info and parts catalogue for the Q5 8R list the expansion valve as a separate component, not an orifice tube.
• Where is the TX-valve on a 2008 Q5 and how long does replacement take?
  It’s mounted at the evaporator connections near the firewall. Labour time varies with access and workshop tooling, but many shops allow roughly 1.5–3.0 hours including recovery, vacuum, and recharge.
• What refrigerant and oil does the 2008 Q5 use?
  R134a refrigerant with the specified PAG oil. Charge mass is shown on the under‑bonnet label, follow that figure for the most accurate fill on local variants.