Parts for your 1999 Toyota Hiace-Tx valve

1999 Toyota Hiace TX Valve — What it does and when to service it

Based on technical references like the Toyota Electronic Parts Catalogue for the H100-series Hiace, the Toyota air-conditioning repair manual for this generation, and DENSO/aftermarket application catalogues used in Australia and New Zealand, the 1999 Toyota Hiace is fitted with a thermal expansion valve (TX valve). Front A/C models use a TX valve at the evaporator, and dual A/C variants typically have a second TX valve for the rear unit. So a TX valve is absolutely relevant to this vehicle.

On a 1999 Hiace, the TX valve meters how much liquid R134a enters the evaporator, responding to evaporator outlet temperature and pressure. By controlling superheat, it keeps the system cooling efficiently without freezing the core. If it sticks or goes out of spec, the van’s air can swing from lukewarm to frosty, and pressures won’t sit where they should.

As part of regular A/C servicing, it’s smart for owners to have a licensed tech evaluate the TX valve’s behaviour via gauge readings and temperature drop across the evaporator. Replacement isn’t a routine interval item, but it’s recommended whenever there’s contamination, a seized compressor event, or if diagnostics point to a metering fault. Because the Hiace uses R134a, any work on the system must be done by a licensed technician (ARCtick in Australia, approved filler/handler in NZ). Always evacuate, replace O‑rings, add the correct PAG oil amount, pull a deep vacuum, and recharge to spec. It’s also good practice to replace the receiver–drier whenever the system is opened or the TX valve is changed.

• Common symptoms of a failing TX valve: poor cooling at idle but OK on the move, frosting on lines/evaporator, vent temps that surge hot–cold, unusually high high-side or low low-side pressures, and compressor short-cycling.
• Service tips: keep the evaporator clean, confirm condenser airflow and fan operation, and verify there’s no moisture in the system. If the Hiace has front and rear A/C, check both TX valves.
• Fitment note: the front TX valve is typically mounted at the evaporator case, access varies by trim and evaporator housing layout.

Done right, a fresh TX valve brings back crisp, stable cabin temps and takes strain off the compressor—perfect for long Aussie or Kiwi runs where the Hiace earns its keep.

Where is the TX valve on a 1999 Toyota Hiace?

It’s mounted at the evaporator assembly. On front A/C models, that’s inside the HVAC/evaporator housing, accessed from the passenger side area. Dual A/C Hiace models usually have a second TX valve at the rear evaporator unit.

What are the signs the TX valve needs replacing?

Fluctuating vent temperatures, weak cooling at idle, frosting on the evaporator or lines, odd pressure readings, and frequent compressor cycling point to a sticky or restricted valve. Proper diagnosis with gauges and temperature probes is key.

Does the 1999 Hiace use R134a and what else should be replaced?

Yes, it uses R134a. Whenever the TX valve is replaced, it’s wise to fit a new receiver–drier, renew O‑rings, add the correct PAG oil, evacuate thoroughly, and recharge to the factory spec.