Parts for your 2009 Audi Q5-Tx valve

2009 Audi Q5 TX‑valve: what it does and how to look after it

Based on technical sources, the 2009 Audi Q5 (type 8R) is fitted with a thermostatic expansion valve (TX‑valve) in its R134a air‑conditioning system. Audi’s parts catalogue (ETKA) lists an “Expansion Valve” for the 8R Q5, commonly referenced as 8K0 820 179 and supersessions, while the Audi workshop information (ElsaWin, Heating/Air Conditioning section) diagrams the valve at the evaporator connections inside the HVAC housing. Major aftermarket catalogues for this model year (e.g., DENSO, Mahle/Behr, Four Seasons) also specify a direct‑fit TX‑valve for the 2009 Q5. So yes, a TX‑valve is relevant on this vehicle.

On the Q5, the TX‑valve meters refrigerant into the evaporator based on temperature and pressure at the outlet, keeping superheat in the sweet spot. That means stable vent temps, no evaporator icing, and efficient cooling even in stop‑start traffic. It works hand‑in‑glove with the variable‑displacement compressor (regulated by the N280 control valve) to balance comfort and load on the engine.

There’s no scheduled replacement interval for the TX‑valve, but it’s smart to check system performance at regular servicing. Telltales that the valve may be sticking or restricted include:

• Sluggish or inconsistent cooling, especially at idle
• Frost on the evaporator line or rapid cycling with hissing at the dash
• Abnormal gauge readings (very low suction or erratic pressures)

If the system’s been open to atmosphere, contaminated, or a compressor has failed, the TX‑valve is often replaced as preventative maintenance along with the receiver‑drier (integrated in the condenser on many Q5s). Always recover the refrigerant properly, replace O‑rings, add the correct PAG oil quantity, evacuate, and recharge to the exact R134a weight shown on the under‑bonnet label. After reassembly, a nitrogen/trace dye leak test and a thorough performance check under different ambient conditions help confirm a tidy job.

Access on the 2009 Q5 is typically via the HVAC case behind the glovebox, where the valve bolts to the evaporator inlet/outlet. Fasteners should be torqued to spec from the workshop manual, and the lines supported to avoid stressing the alloy fittings. Used with clean refrigerant, the right oil, and a healthy condenser fan setup, the TX‑valve will usually run for years without fuss.

Popular questions

Does the 2009 Audi Q5 use a TX‑valve or an orifice tube?
It uses a thermostatic expansion valve. Audi’s ETKA parts listings and the factory HVAC diagrams for the 8R Q5 show a dedicated expansion valve at the evaporator, not a fixed orifice tube.

Where is the TX‑valve located on a 2009 Q5?
It’s mounted at the evaporator connections inside the HVAC housing, generally accessed from behind the glovebox area. The liquid and suction lines pass through the firewall and bolt to the valve at that point.

When should the TX‑valve be replaced?
There’s no routine interval. Replace it if there are symptoms of restriction or sticking, during major A/C repairs, or after contamination events (like a compressor failure). Many techs renew it together with the receiver‑drier when the system’s opened.