Parts for your 1999 Mitsubishi Lancer-Tx valve

1999 Mitsubishi Lancer TX Valve — What it does and when to service it

Based on Mitsubishi’s technical documentation for the CK/CE-series Lancer (covering 1996–2002) and the Mitsubishi ASA/EPC parts catalogue, the 1999 Mitsubishi Lancer’s air-conditioning system uses a thermostatic expansion valve (TX valve) at the evaporator inlet, not an orifice tube. These sources describe the valve’s location at the evaporator and include procedures for replacement and sealing, confirming the TX valve is relevant to this model.

On a 1999 Lancer, the TX valve’s job is to meter liquid R134a into the evaporator while responding to outlet temperature and pressure. By holding the right superheat, it keeps the evaporator cold without icing, stabilises vent temperatures, and helps the compressor work efficiently in Aussie and Kiwi conditions. When the valve sticks or goes out of calibration, the cabin can swing from lukewarm to frosty, the evaporator can frost up, or cooling can fade at idle.

There’s no routine replacement interval for the TX valve, it’s changed on condition. A licensed A/C technician should diagnose properly, because similar symptoms can come from low refrigerant, a weak condenser fan, or a restricted drier. If the valve is confirmed faulty or the system’s been contaminated (for example after a compressor failure), replacement is recommended.

• Typical clues the Lancer’s TX valve may be the culprit:
  • Inconsistent vent temps, especially after warm restarts
  • Frosting at the evaporator or on the suction line
  • Hissing and rapid cycling with abnormal high/low side pressures

Best-practice replacement on this model involves recovering the refrigerant, accessing the valve at the evaporator inlet (at the firewall, some trims require glovebox/evaporator cover removal for the fasteners), renewing HNBR O-rings lightly lubricated with the correct compressor oil, and torquing the fittings to spec from the workshop manual. Any time the system is opened, the receiver–drier should be replaced, the system evacuated to deep vacuum, and then recharged by weight to the under-bonnet label. A nitrogen pressure test and a post-service leak check are smart moves.

If the compressor has failed, the lines and condenser should be assessed for debris and flushed or replaced as needed, otherwise, avoid flushing the TX valve itself—replace it. Always use the oil type and charge weight specified for the Lancer’s compressor variant. In Australia and New Zealand, refrigerant handling must be carried out by a licensed technician.

Where is the TX valve on a 1999 Lancer?

It’s mounted at the evaporator inlet on the firewall where the A/C lines pass through. Access is typically from the engine bay to disconnect the lines, and from the passenger side to reach the valve fasteners on the evaporator block. Some trims need the glovebox and an evaporator cover removed.

How often should the TX valve be replaced?

There’s no set interval. It’s a replace-on-failure part. If cooling is inconsistent and pressures indicate metering issues—and other causes are ruled out—replacement makes sense. Replace the receiver–drier whenever the system is opened and regas to the specified charge by weight.

What are the signs of a failing TX valve on this model?

Weak or fluctuating cooling, evaporator icing, rapid compressor cycling, or odd pressure readings with normal condenser fan operation. A proper diagnosis with gauges and temperature checks by a licensed tech will confirm whether the valve is sticking or restricted.