Parts for your 2017 Audi Q5-Tx valve

2017 Audi Q5 TX valve — what it does and when to replace it

Based on Audi’s technical literature and parts data (ETKA parts catalogue and ELSA workshop manual for the 2017 Q5, type 8R), this model uses a thermostatic expansion valve (TX valve), also known as an H‑valve, mounted at the evaporator inlet. Typical OE part references for this platform include 8T0 820 679 and supersessions, which vary by VIN. So yes—this vehicle is built with a TX valve and relies on it for proper air‑conditioning performance.

The TX valve meters liquid refrigerant into the evaporator, reacting to evaporator outlet temperature and pressure to keep a small, stable amount of superheat. That balance stops the evaporator freezing, protects the compressor from liquid slugging, and helps the Q5 deliver consistent cabin temps from city traffic to open‑road kilometres. On the 2017 Q5’s variable‑displacement compressor setup and condenser with integrated drier, the TX valve is the key control point for refrigerant flow into the cabin heat exchanger.

There’s no routine “service” for a TX valve, but it can fail or become restricted by debris or moisture. Common clues include weak cooling at idle, temperature swings, frost or sweating at the firewall unions, hissing, or pressure readings that show a starved evaporator. If the system’s been open to air, had a compressor failure, or shows contamination, the valve can stick or ice internally.

When replacement is needed, a licensed A/C technician (ARCtick in Australia or an approved handler in New Zealand) should recover the refrigerant, isolate the lines at the firewall, and swap the valve with new O‑rings. If there’s evidence of metal or sludge, follow Audi repair guidance: flush where permitted, replace the receiver‑drier element (often integrated with the condenser on this model) as required, renew the cabin filter, evacuate, leak‑test, and recharge by weight with the refrigerant specified on the under‑bonnet label (R134a or R1234yf, market‑dependent). Always torque fasteners to factory spec from the workshop manual.

Owners can help the system by keeping the condenser face clean and replacing the pollen filter on schedule. But if cooling is patchy or the system is noisy, it’s worth a proper diagnosis—TX valve faults can mimic low charge or a weak compressor, and a quick gauge check can save guesswork.

• Typical symptoms: erratic vent temps, low cooling at idle, frosting at firewall, abnormal pressure readings.
• Best practice on replacement: new O‑rings, correct oil balance, vacuum, leak test, recharge by weight.

Does the 2017 Audi Q5 have a TX valve?

Yes. Audi’s ETKA parts catalogue and ELSA workshop procedures list a thermostatic expansion (H‑) valve at the evaporator inlet on the 2017 Q5 (8R). It’s the metering device that controls refrigerant flow into the evaporator.

What are the signs the TX valve is failing on a 2017 Q5?

Look for weak cooling at idle, rapid temperature swings, frost or sweating at the firewall fittings, and system noises. On gauges, you’ll often see a starved evaporator or unstable low‑side pressure. These can also point to charge issues, so a proper diagnosis is essential.

How much does a TX valve replacement cost?

Parts typically sit around AUD/NZD $120–$300, with 2–4 hours labour depending on access and corrosion. Add refrigerant recovery and re‑gas ($150–$300). Expect a ballpark of AUD $500–$1,200 or NZD $600–$1,400, varying by workshop and what else the system needs (e.g., drier element).