Parts for your 2006 Holden Commodore-Tx valve

2006 Holden Commodore TX valve: what it does, where it lives, and when to sort it

For the 2006 Holden Commodore (late VZ and early VE builds), the factory air‑con system uses a thermostatic expansion valve (TX valve) at the evaporator, not an orifice tube setup. This is documented in Holden’s VZ and VE Service/Workshop Manuals (HVAC sections), GM Holden SI service procedures for A/C diagnosis and repair, and HVAC technical references from DENSO on TXV operation. Those sources describe the TX valve regulating refrigerant flow into the evaporator and being mounted at the evaporator inlet in the HVAC case (often the H‑block style on the firewall/bulkhead connections).

The TX valve’s job is simple but critical: it meters liquid R134a into the evaporator to maintain the right superheat. Do it well, and the cabin gets cold quickly without freezing the core. When it sticks or drifts out of spec, the Commodore can swing between lukewarm and frosty, cycle the compressor too often, or show uneven vent temps.

Common signs the TX valve needs attention include:

• Weak cooling at idle that’s a tad better on the move
• Frost or sweat on the evaporator pipes near the firewall
• Hunting compressor cycling or high/low pressure readings out of whack on gauges
• Hiss or chatter at the valve after start-up

As part of servicing, a licensed tech (ARCtick in AU/NZ) should inspect for oil stains at the valve block, check superheat/pressures, and confirm charge by weight to the under‑bonnet decal. If replacing the TX valve, best practice per GMH procedures is to:

1. Recover refrigerant, then remove the valve and lines without twisting the evaporator stubs
2. Fit new compatible O‑rings lubricated with the correct PAG oil
3. Replace the receiver‑drier (drier) whenever the circuit’s opened, especially after a valve failure
4. Vacuum to deep level and hold to confirm no leaks or moisture
5. Recharge with the specified R134a weight and verify vent temps and stability

Because access is at the firewall/bulkhead on most 2006 Commodores, the job’s usually straightforward, but cramped. If there’s debris or burnishing from a worn compressor, the system may need flushing or component replacement before a new TX valve goes in—DENSO and GMH guidance both warn that contamination will quickly upset a fresh valve.

Technical references: Holden VZ/VE Service and Workshop Manuals (HVAC/Air Conditioning sections), GM Holden Service Information (A/C diagnostics and repair), and DENSO Air Conditioning Fundamentals on TXV function and symptoms.

Popular questions

Where’s the TX valve on a 2006 Commodore?
It’s mounted at the evaporator inlet in the HVAC housing, typically where the two A/C pipes meet the firewall/bulkhead. You’ll see an alloy H‑block with two line connections and a sensing element—accessed from the engine bay on most variants.

Do I need to replace the drier when changing the TX valve?
Yes, it’s strongly recommended. Opening the system lets in moisture, and a tired drier won’t protect the fresh valve. GMH procedures call for a new receiver‑drier and O‑rings any time major A/C components are replaced.

How do I tell if it’s a bad TX valve or just low gas?
Low refrigerant often gives weak cooling across all conditions with bubble‑filled sight lines (if fitted) and low static pressure. A faulty TX valve can show normal charge but unstable pressures, frost on the outlet pipe, or uneven vent temps. Proper diagnosis needs manifold gauges and superheat checks.