Parts for your 2018 Subaru Impreza-Tx valve

2018 Subaru Impreza TX valve (A/C expansion valve)

Yes, the 2018 Subaru Impreza uses a TX valve (thermostatic expansion valve) in its air‑conditioning system. This is documented in Subaru’s service literature (Subaru Technical Information System workshop manual for the GK/GT Impreza, Air Conditioner System section), and it’s also listed as “Expansion Valve” in the genuine Subaru electronic parts catalogue for MY2018 Impreza models. OE supplier data for this platform (DENSO A/C system architecture) likewise specifies a block‑type TXV at the evaporator rather than a fixed orifice tube.

The TX valve’s job is to precisely meter refrigerant into the evaporator based on temperature and pressure feedback, keeping the evaporator just cool enough to absorb heat without letting liquid refrigerant reach the compressor. That control maintains stable cabin temps, prevents evaporator icing, and protects the compressor from liquid slugging. On the 2018 Impreza it’s mounted at the evaporator connection on the bulkhead, where the A/C pipes pass through the firewall, making access possible from the engine bay.

It isn’t a routine replacement item, but it does benefit from proper checks during air‑con servicing. If cooling is weak at idle, if the system ices up, or if pressure readings are skewed (low suction with normal/high discharge or vice versa), the TX valve might be sticking or restricted. Before condemning it, a good tech will rule out low refrigerant charge, a clogged cabin filter, weak condenser airflow, or a failing compressor control valve.

• Service pointers for the Impreza’s TX valve:
  • Only open the system with proper recovery equipment and keep everything clean and capped to avoid moisture ingress.
  • Replace the O‑rings and torque the fittings to the Subaru spec, use the exact refrigerant oil type and quantity specified by Subaru.
  • Evacuate and recharge with the correct R‑1234yf charge by weight (check the under‑bonnet label).
  • If the system has been open or contaminated, replace the condenser’s desiccant element/assembly as recommended by Subaru.

When replacement is necessary (contamination, internal debris, or a clearly failed valve), it’s sensible to inspect the lines for debris, flush where allowed, and confirm condenser and fan performance. Done right, the TX valve will keep the Impreza’s air‑con crisp through hot Aussie and Kiwi summers and those damp winter demist mornings.

Where is the TX valve on a 2018 Subaru Impreza?

It sits at the evaporator connection on the firewall/bulkhead, where the refrigerant lines pass from the engine bay into the cabin. Access is from the engine bay, some trim or components may need to be moved for working room.

What are common symptoms of a failing TX valve?

Intermittent or weak cooling, especially at idle or in traffic, evaporator or line icing, rapid cycling, and unusual pressure readings. A restricted valve can give low suction pressure and poor cooling, a stuck‑open valve can flood the evaporator and risk compressor damage.

Should the TX valve be replaced during major A/C repairs?

Not automatically. It’s best practice to replace the desiccant when the system is opened and to flush/inspect for debris. Replace the TX valve if there’s evidence of contamination, corrosion, or sticking, or when a compressor failure (“black death”) has occurred.