Parts for your 2005 Nissan Serena-Tx valve

2005 Nissan Serena TX Valve — what it does and when to replace it

Based on the Nissan Serena C25 factory service manual (HA/Heater & Air Conditioning), the Nissan FAST electronic parts catalogue, and Denso A/C application data, the 2005 Serena uses a thermal expansion valve (TXV) on the front evaporator. Models with dual air (rear cooler) also have a second rear TXV mounted at the rear evaporator. So yes, a TX valve is absolutely relevant to the 2005 Nissan Serena’s R134a air-con system.

The TX valve meters liquid refrigerant into the evaporator, matching flow to heat load so the evaporator runs cool without flooding. In plain speak, it’s the bit that keeps vent temps chilly without icing the core. When the TXV sticks or drifts out of spec, you’ll cop lukewarm air, frosty pipes, or compressor cycling that feels all wrong in Kiwi or Aussie summer traffic.

During routine A/C servicing, a healthy TXV doesn’t need regular replacement, but it does rely on a clean, correctly charged system. Any time the circuit has been open (after a condenser, compressor or hose swap), it pays to replace the receiver–drier and new O‑rings, evacuate properly, and recharge to the label spec. If the Serena has rear air, remember there can be two TXVs and two evaporators, so diagnosis should confirm whether the front, rear, or both are misbehaving.

• Common signs of a crook TXV: weak cooling at idle, evaporator icing, low-side vacuuming too hard, or uneven vent temps front vs rear (on dual A/C models).
• Before blaming the valve, verify condenser airflow, fan operation, charge mass, and that the drier isn’t saturated.
• When replacing: recover refrigerant with a licensed tech, fit the correct block-style TXV, replace O‑rings, lightly oil seals with the specified PAG oil, evacuate, then recharge.
• Contamination kills TXVs. If a compressor let go, flush lines and consider replacing both TXVs on dual systems.

Access on the Serena’s front unit is typically at the evaporator case (engine bay side/firewall area), while the rear TXV sits in the rear HVAC box. It’s a good idea to pressure-test with nitrogen after reassembly, then pull a deep vacuum and verify stable microns. Done right, a fresh TX valve restores crisp, consistent cabin temps and takes strain off the compressor, saving fuel and keeping everyone comfy on those long coastal runs.

• Does a 2005 Nissan Serena have a TX valve or an orifice tube?
  It uses TX valves. There’s a block-type TXV on the front evaporator, and if the vehicle has rear air, a second TXV is fitted at the rear evaporator. This layout is confirmed in the Nissan C25 Serena service manual and parts catalogue.
• What are the symptoms of a failing TX valve on a Serena?
  Expect poor cooling at idle, evaporator icing, a wildly low low-side pressure, or big differences between front and rear vent temps on dual A/C models. Rule out low refrigerant, blocked drier, or weak condenser fans before condemning the valve.
• Do I need to regas after replacing the TX valve?
  Yes. The system must be recovered, opened to change the valve and O‑rings, then pressure-tested, evacuated, and recharged with the specified R134a amount. The exact charge varies by front-only vs dual A/C, so follow the under‑bonnet label or service data.