Parts for your 2019 Nissan Serena-Tx valve

2019 Nissan Serena TX Valve: what it does, and when to service it

Based on technical sources, the 2019 Nissan Serena (C27) uses thermal expansion valves (TX valves) in its air-conditioning system. The Nissan Serena C27 Series Service Manual (Heater & Air Conditioning — HA section, 2018–2019 editions) identifies “Expansion Valve — Front” and, on dual A/C models, “Expansion Valve — Rear” at the evaporators. The Nissan FAST Electronic Parts Catalogue for C27 likewise lists expansion valve components for front and rear circuits. These references confirm a TX valve is fitted and relevant to A/C service on this model.

On the 2019 Serena, the TX valve meters liquid refrigerant into the evaporator, responding to outlet temperature and pressure to maintain the ideal superheat. Put simply, it’s the clever bit that keeps cabin temps stable without flooding or starving the evaporator. Most Serena C27s run a DENSO variable-displacement compressor and sub-cool condenser, and the TX valve is matched to that setup to keep performance up while reducing compressor load — handy for fuel economy and hybrids like e-POWER.

There’s no scheduled replacement interval for a TX valve. It’s usually replaced only if it’s sticking, blocked with debris, or leaking. Tell-tale signs include weak cooling at idle but cooler air on the move, frosting on the evaporator pipes near the firewall, a noisy or hunting compressor, and gauge readings showing very low suction with normal/high discharge. On dual A/C Serenas, poor rear cooling can point to the rear TX valve.

Replacement is a straightforward but strictly licensed A/C job. A tech will recover the refrigerant, access the valve (front unit is typically at the front evaporator behind the dash, rear unit is in the rear quarter trim on dual A/C models), and swap it with new O-rings lubricated in the correct refrigerant oil. Best practice with any contamination or compressor failure is to replace the receiver–drier (integrated in the condenser on many C27s), flush lines as specified, evacuate for the recommended duration, and recharge by weight with the label-specified refrigerant (some markets use R-134a, others use R-1234yf).

A couple of practical tips owners appreciate:

• If cooling is inconsistent, have a workshop run pressure and temperature diagnostics before green-lighting parts replacement — sensors or blend doors can mimic TX valve faults.
• Any time the system is opened, use new O-rings, observe cleanliness, and verify there are no leaks with nitrogen or an approved leak detector before recharging.

Popular questions about the 2019 Nissan Serena TX valve

Does the 2019 Serena use R-134a or R-1234yf?
It varies by market and build. The under‑bonnet A/C label is the decider. Many Japan‑domestic C27s transitioned to R‑1234yf around this period, while some export markets retained R‑134a. Charge by the exact weight shown on the vehicle label.

Where is the TX valve on a 2019 Serena?
The front TX valve is mounted at the front evaporator (behind the dash, typically accessed from the passenger side). On dual A/C models, there’s a second TX valve at the rear evaporator, usually behind the right‑hand rear quarter interior trim.

Should the receiver–drier be replaced when changing the TX valve?
If the circuit has been open to atmosphere or there’s been compressor or debris contamination, yes — replace the drier (often built into the condenser on the C27). This helps protect the new valve and restores proper moisture control.