Parts for your 2018 Mazda 3-Tx valve

2018 Mazda 3 TX Valve: What it does and how to look after it

Technical sources confirm the 2018 Mazda 3 runs a thermal expansion valve (TXV). The Mazda3 (BM/BN) Workshop Manual lists “Expansion Valve—Removal/Installation” within the HVAC section, and the Mazda Electronic Parts Catalogue for 2018 BM/BN models shows a block-type TXV mounted at the evaporator. DENSO OE application data for BM/BN platforms likewise specifies a TXV system rather than an orifice-tube setup. So a TX valve is absolutely relevant and fitted to the 2018 Mazda 3.

On this model, the TXV meters refrigerant into the evaporator, keeping superheat in check so the core does maximum cooling without liquid slugging the compressor. Because it responds to load and temperature changes—think stinking hot arvo in traffic versus a cool morning commute—it helps maintain steady vent temps and protects the A/C hardware. It’s a compact, block-style valve at the evaporator inlet, working with a receiver–drier integrated into the condenser. Depending on build spec, the car uses R‑134a or R‑1234yf, the under‑bonnet label calls this out along with the exact charge.

There’s no scheduled “service” for the TXV itself, but it’s central to A/C performance. Symptoms pointing to a crook valve include weak cooling especially at idle, rapid swings in vent temperature, frosting on the low-side line at the firewall, or pressure readings that are too high or too low for the ambient conditions. Contamination (desiccant debris or metal after a compressor failure) can jam the valve, so if the system’s been open or suffered a major fault, a proper clean-out matters.

When replacement is needed, best practice is to have an ARCtick-licensed technician recover the refrigerant, replace the TXV and O-rings, and renew the desiccant in the condenser if the system’s been contaminated or open to air. Lines should be flushed where appropriate, correct PAG oil balance restored, and the system evacuated and recharged by weight. After refit, a leak test and a performance check (vent temps and pressure readings against the workshop spec) help verify it’s all sweet. Keeping the cabin filter fresh and the condenser face clean also reduces strain on the valve by improving airflow across the system.

• Tell‑tale faults: erratic cooling, line frosting, odd hissing, abnormal gauge readings.
• Always replace O‑rings, lubricate with the correct oil, and torque fittings to the workshop spec.
• If the compressor’s failed, expect TXV replacement plus system clean, new desiccant, and careful re‑oil.

FAQs

Does the 2018 Mazda 3 have a TX valve or an orifice tube?
The 2018 Mazda 3 uses a thermal expansion valve (TXV) at the evaporator, not an orifice tube. This is documented in the Mazda3 (BM/BN) Workshop Manual and shown in the Mazda EPC for 2018 models.

What are common signs the TX valve is failing on a 2018 Mazda 3?
Weak or inconsistent cooling, frosting on the suction line near the firewall, unusual hissing, and high/low pressure readings that don’t match ambient conditions. After contamination or a compressor issue, the TXV can stick or plug.

How much does a TX valve replacement typically cost?
Parts generally sit around AUD/NZD $80–$220 for quality OE‑equivalent units, with 2–4 hours labour depending on access and testing. With refrigerant, oil balancing, and any desiccant renewal, total jobs often land in the AUD/NZD $400–$900 range.