Parts for your 2009 Subaru Legacy-Tx valve

2009 Subaru Legacy TX Valve: purpose, fitment, and service advice

Based on Subaru’s Factory Service Manual (HVAC section for the BL/BP chassis), the 2009 Subaru Legacy uses a thermostatic expansion valve (TX valve) at the evaporator inlet to meter refrigerant. Subaru’s parts catalogue (often referenced via the Subaru FAST system) lists an A/C “Valve – Expansion” for 2005–2009 Legacy/Outback models (e.g., 73520AG00A/73520AG01A), and common OE-supplier catalogues (DENSO and reputable aftermarket like Four Seasons/UAC) provide matching TX valves for this vehicle. So a TX valve is relevant and fitted to the 2009 Legacy.

The TX valve’s job is to control how much R134a enters the evaporator, responding to outlet temperature and pressure to keep the evaporator at the sweet spot for heat absorption. When it’s doing its thing, cabin temps stay steady and cool without the compressor working overtime. If it sticks or drifts out of spec, owners may notice weak cooling at idle, frosty lines, or temperature swings that are a bit all over the shop.

There’s no routine “maintenance” for a TX valve, but keeping the A/C system clean and dry helps it live a long, drama‑free life. That means replacing the cabin filter on schedule to maintain airflow across the evaporator, running the air‑con regularly through the year, and ensuring any refrigerant work is done with clean tools and proper evacuation to keep moisture out.

When replacement is on the cards, it’s a professional job in Australia and New Zealand because refrigerant recovery is a licensed activity. The valve sits on the HVAC case at the firewall where the A/C pipes pass through, bolted to the evaporator inlet and outlet. A proper service will typically include:

• Recovering the refrigerant, then removing the lines and the valve.
• Fitting new O‑rings lubricated with the correct refrigerant oil.
• Inspecting the evaporator and pipes for debris or corrosion.
• Evacuating the system, checking for leaks, and recharging by weight per the under‑bonnet label.
• Replacing the receiver‑drier/desiccant (integrated with the condenser on many models) whenever the system has been opened.

Tell‑tale signs it’s time to check the TX valve include poor cabin cooling at low speeds, evaporator or suction line icing, hissing at the dash, and high/low side pressures that don’t track with ambient. A competent tech will confirm with gauges and temperature readings before calling the part.

Popular questions about the 2009 Subaru Legacy TX valve

Where is the TX valve located on a 2009 Subaru Legacy?
The TX valve is mounted at the evaporator inlet on the HVAC case, right where the A/C lines pass through the firewall. Access typically involves working from the engine bay side and, on some jobs, partially loosening the HVAC case fittings.

What are the symptoms of a failing TX valve on this model?
Common signs are weak or inconsistent cooling, especially at idle, occasional frost on the suction line, and vent temperatures that swing hot–cold. A technician’s gauge set may show low suction with normal to high discharge, or hunting pressures as the valve sticks.

Do they need to regas the air‑con after replacing the TX valve?
Yes. The system must be evacuated to remove air and moisture and then recharged by weight with R134a and the specified oil quantity. In AU/NZ this is a licensed procedure and is best paired with a desiccant replacement if the system has been open.