Parts for your 2014 Nissan Serena-Tx valve

2014 Nissan Serena TX Valve — what it does, where it lives, and when to service it

For the 2014 Nissan Serena (C26 series), a TX valve (thermostatic expansion valve) is indeed fitted. Technical references including the Nissan Serena C26 Electronic Service Manual (HA: Heater & Air Conditioning section) and the Nissan FAST/EPC catalogue list expansion valves for both the front and the optional rear A/C units on this model. OE supplier catalogues for the C26 platform also specify TX valves rather than fixed orifice tubes, confirming this vehicle uses TXV-based refrigerant control.

The TX valve meters refrigerant into the evaporator based on temperature sensed at the outlet, keeping superheat in the right window so the system cools hard without flooding the compressor. On Serena models with dual air, there are two TX valves: one at the front evaporator case and another at the rear unit. That setup helps keep cabin temps consistent from the first row to the back seats — handy for school runs and long roadies.

Over time, a TX valve can stick, clog with debris from compressor wear, or drift off-spec. Typical tells include slow or uneven cooling, frosty lines or an iced-up evaporator, hissy/whistly operation, or pressures that swing around when checked on gauges. If the compressor has carked it or the system’s been contaminated, the TX valve is high on the list to replace.

Replacement is a job for a licensed air-con technician (ARCtick-authorised in Australia), because the system must be properly recovered, evacuated and recharged to the R134a quantity on the under-bonnet label. Standard best practice is to renew the HNBR O‑rings, torque the valve to spec from the service manual, replace the receiver/drier if contamination is suspected, and add the correct PAG oil balance. After fitting, the tech will vacuum-test, leak-check, and recharge — then confirm vent temps and pressure behaviour. For dual A/C Serenas, the rear TX valve sits with the rear evaporator assembly (accessed behind interior trim), while the front valve is mounted at the evaporator case near the firewall.

Day to day, there’s not much “maintenance” for a TX valve beyond prevention: keep the cabin filter fresh, the condenser clean, and run the A/C regularly year-round to move oil through the system. If cooling drops off, get it pressure-tested rather than just “regassed” — topping up without fixing a leak or a sticky valve is a short-lived fix.

• Common TX valve symptoms on Serena: weak cooling, temperature swings, icing at the valve/evap, unusual hissing, or abnormal gauge readings.
• Service tips: replace O-rings, use correct oil, vacuum and charge to spec, and consider the drier if there’s debris or moisture.

Where is the TX valve on a 2014 Nissan Serena?

On front A/C, it’s mounted at the evaporator case near the firewall area. If the van has rear A/C, there’s a second TX valve integrated with the rear evaporator unit, typically accessed behind rear quarter interior trim. Panels and lines vary slightly by trim, so a workshop manual helps with exact access steps.

What are the signs the TX valve needs replacing?

Expect poor or inconsistent cooling, frost on the evaporator or valve, hissing at the case, and odd high/low-side pressures. After a compressor failure or if desiccant breaks down, debris can jam the valve — that’s a prime time to fit a new one.

Do both front and rear TX valves need replacing together?

Not always. They can be serviced individually based on diagnosis. That said, if the system’s been contaminated or the compressor failed, it’s smart to assess both valves and the drier, and flush where the service manual allows.