Parts for your 1999 Toyota Avensis-Tx valve

1999 Toyota Avensis TX valve: what it does and how to look after it

Based on technical references including the Toyota Avensis (T22) Repair Manual – Air Conditioning (Cooling Unit) section, the Toyota Electronic Parts Catalogue listing “Valve Sub‑Assy, Cooler Expansion,” and OE supplier catalogues from DENSO/Nissens for 1997–2003 Avensis models, the 1999 Toyota Avensis is fitted with a thermostatic expansion valve (TX valve) at the evaporator inlet. So yes, a TX valve is relevant on this vehicle.

The TX valve on a ’99 Avensis meters refrigerant into the evaporator, reacting to suction line temperature and pressure to keep superheat in the sweet spot. When it’s on song, vent temps stay nice and cold without icing the core, even on a scorching arvo. When it plays up—sticking open or shut, or getting blocked by debris or moisture—you’ll see weak cooling, frosty lines, noisy hissing near the dash, or temperatures that bounce around on a long drive.

It’s not really a “service item” like a filter, it’s replaced when there are symptoms or whenever the A/C circuit is opened for major work. On the Avensis, the TX valve sits on the evaporator in the HVAC case behind the glovebox. Replacement means recovering the R134a, removing the glovebox and cooler unit access, unbolting the valve from the evaporator block, and fitting a quality replacement with new green HNBR O‑rings lightly oiled with the correct PAG oil. The system should be evacuated with a vacuum pump to boil off moisture, then recharged to the factory weight on the under‑bonnet label by a licensed A/C tech, as required by AU/NZ regulations.

Best practice is to replace the receiver/drier (or desiccant element, if serviceable) whenever the circuit’s opened. If the old valve showed signs of contamination, flushing the lines and checking the condenser and compressor for debris is a smart move. A cabin filter in good nick (where fitted) helps airflow and reduces the chance of evaporator icing that can mask TX valve issues.

If the Avensis cools fine at speed but not at idle, or if pressures look odd on gauges, a tech will confirm TX valve behaviour with pressure/temperature readings and superheat checks. Don’t overtighten the small valve fasteners—use the Toyota torque spec and alignment dowels to avoid leaks. With the right parts and procedures, a fresh TX valve brings back crisp, reliable cooling that lasts for years.

• Replace O‑rings and drier whenever the system is opened.
• Vacuum, leak test, and charge by weight to the spec label.
• Have A/C work carried out by a licensed technician.

Where is the TX valve on a 1999 Toyota Avensis?

It’s mounted at the evaporator inlet inside the HVAC case, behind the glovebox. Access is through the passenger side once the glovebox and trim are removed. The valve bolts directly to the evaporator block where the two A/C pipes pass through the firewall.

What are the signs a TX valve needs replacing?

Common clues include poor cooling at idle, frost on the evaporator outlet or suction line, fluctuating vent temperatures, a noticeable hiss near the dash, or abnormal gauge readings (very low suction or unusually high suction with warm vents). A licensed tech can confirm with pressure and temperature checks.

Is the TX valve a regular service item?

No. It’s replaced if faulty or when the system is opened for major A/C repairs. During any TX valve job, new O‑rings and a fresh receiver/drier are recommended, along with a proper vacuum and a charge to the specified weight.