Parts for your 2020 Nissan Serena-Tx valve

2020 Nissan Serena TX-valve: what it does and how to look after it

Based on the Nissan Serena C27 Series Service Manual (HA – Heater & Air Conditioning) and the Nissan FAST electronic parts catalogue, the 2020 Nissan Serena is fitted with thermal expansion valves (TX-valves). Dual A/C models have a front TX-valve at the HVAC unit and a rear TX-valve at the rear evaporator. So yes, a TX-valve is relevant to this vehicle.

In the Serena’s air-con system, the TX-valve meters how much liquid refrigerant enters the evaporator, using temperature and pressure at the evaporator outlet to keep superheat in the sweet spot. That control stops the evaporator from icing up, protects the compressor from liquid slugging, and keeps cabin temps steady. With the Serena’s available dual-zone (front/rear) setup, each evaporator gets its own valve so passengers in all rows stay comfy even on stinking hot days.

The TX-valve isn’t a “service item”, but it can fail or get contaminated. Typical clues include weak cooling at idle, chilly one minute and warm the next, frosting on lines at the firewall or rear quarter, odd hissing, or pressure readings that don’t stack up (very low low-side / very high high-side, or vice versa). Oil or dye traces at the valve fittings point to a seal issue.

Replacement is straightforward for a licensed A/C tech but involves the right gear. The correct approach is:

• Recover the refrigerant, not vent it.
• Remove and replace the TX-valve and all related O-rings, inspect the rear unit on dual A/C models.
• Vacuum, leak-test, and recharge to the exact spec on the under‑bonnet label (refrigerant type and weight), adding the correct PAG oil amount.
• If the system’s been open to air, replace or service the drier/desiccant as recommended.

Good practice to extend TX-valve and system life:

• Run the A/C regularly year‑round to keep seals lubricated.
• Keep the cabin filter fresh so airflow over the evaporator stays healthy.
• Use the specified refrigerant and oil only, mixing types is a fast track to valve and compressor grief.
• Have A/C work done by an ARCtick‑licensed pro (AU) or a certified refrigerant handler (NZ).

Access notes for the Serena: the front TX-valve sits at the HVAC case behind the dash area, the rear valve (if fitted) is near the rear evaporator in the left rear quarter trim. Labour can vary depending on trim and access, so budgeting for both diagnosis and re-gassing is wise.

Popular questions about the 2020 Nissan Serena TX-valve

Does the 2020 Serena have one or two TX-valves?
Most dual A/C models have two: one for the front evaporator and one for the rear. Single-zone versions use just the front TX-valve. The Nissan HA service manual and FAST parts listings show expansion valves at both evaporators on dual systems.

When should the TX-valve be replaced?
Only when it’s faulty or contaminated—there’s no routine interval. If symptoms point to a sticking or blocked valve, replacement is done with full refrigerant recovery, new O-rings, vacuum, and a precise recharge. Expect fresh dye/oil as needed and a leak test before handing the keys back.

Does a 2020 Serena use R134a or R1234yf?
It depends on market and build. Always follow the under‑bonnet label for the correct refrigerant type and charge weight. Never mix refrigerants, and don’t guess—using the wrong gas or quantity can damage the TX-valve and compressor.