Parts for your 2007 Toyota Ist-Tx valve

2007 Toyota ist TX-valve: what it does and how to look after it

Based on technical sources, the 2007 Toyota ist is fitted with a TX-valve (thermal expansion valve). Toyota’s Electronic Parts Catalogue for the NCP110/NCP115 ist lists a “Valve, Cooler Expansion” at the evaporator inlet, and the factory A/C service manuals for the platform twin (Scion xD/Toyota ist NCP110) show a TX-valve and receiver-drier style system rather than an orifice-tube/accumulator layout. DENSO and major aftermarket catalogues also specify an A/C expansion valve for the 2007–on ist. So yes—this model uses a TX-valve.

The TX-valve’s job is to meter refrigerant into the evaporator based on temperature and pressure, so the air-con cools efficiently without flooding or starving the core. On the 2007 ist it’s mounted at the evaporator outlet/inlet union, typically behind the dash on the cabin side of the firewall. When it’s working right, cabin temps drop quickly and the system cycles smoothly, when it’s unhappy, cooling is patchy, pressures go wonky, and the compressor can get cranky.

During servicing, it’s smart to think of the TX-valve as part of the bigger A/C picture. If the system’s been open to atmosphere, contaminated, or a compressor has failed, replacing the TX-valve along with the receiver-drier and all disturbed O-rings is considered best practice. The valve’s tiny passages can clog with debris or moisture, leading to low cooling or icing. Because replacement means opening the refrigerant circuit, the job needs an ARCtick-certified tech in Australia or a certified handler in New Zealand. Proper recovery, evacuation, leak testing, and an accurate recharge by weight are essential. Use only the refrigerant and oil type specified on the under-bonnet label for this vehicle, add the correct oil amount to compensate for component replacement.

Common clues the TX-valve may be due are:

• Poor or intermittent cooling, especially at idle or in traffic
• Evaporator or lines icing, hissing, or chirping
• High or uneven pressure readings on gauges
• Compressor short-cycling or staying engaged too long

If the dash needs to come out to access the valve, many owners tie the job to other interior or HVAC maintenance to save labour. After fitting a new TX-valve, always replace the sealing washers/O-rings, torque to spec, evacuate to a deep vacuum, and verify superheat/subcooling where applicable. A quick post-repair performance test—centre vent temps, stable pressures, and no frost where it shouldn’t be—gives confidence the ist’s air-con is ready for a long, hot summer.

Popular questions about the 2007 Toyota ist TX-valve

Where is the TX-valve located on a 2007 Toyota ist?
It’s fitted at the evaporator connection, typically behind the dashboard on the passenger side, close to the firewall. Access usually requires removing parts of the glovebox/centre panels, and in some cases more extensive dash trim.

Because access is tight and the system must be opened and re-gassed, most workshops treat it as a professional job rather than DIY.

What are the signs my TX-valve needs replacing?
Weak cooling, air that’s cold then suddenly warm, ice forming on the evaporator or lines, and odd pressure readings are classic symptoms. A noisy or overworked compressor can also be a clue, but a gauge set and proper diagnosis are needed to rule out low refrigerant, a blocked drier, or a weak compressor.

Should the receiver-drier be changed with the TX-valve?
Yes. Best practice on this vehicle is to replace the receiver-drier whenever the system is opened for major work, including TX-valve replacement. It traps moisture and debris, leaving an old drier in place can contaminate the new valve and reduce performance.