Parts for your 1989 Mitsubishi Pajero-Tx valve

1989 Mitsubishi Pajero TX‑Valve: What It Does, Where It Lives, and How to Look After It

Yes, the 1989 Mitsubishi Pajero uses a thermostatic expansion valve (TX‑valve) in its air‑conditioning system. This is shown in the Mitsubishi Pajero/Montero Workshop Manual (HVAC section for late‑80s models), which depicts a TX‑valve at the evaporator inlet, and in Mitsubishi’s ASA parts catalogue for L0/L1 series Pajero models listing an “Expansion Valve, Evaporator.” It also aligns with MACS training materials noting that Japanese R12‑era systems typically use a TX‑valve with a receiver‑drier rather than an orifice tube with an accumulator.

The TX‑valve is the little brain of the Pajero’s A/C. It meters refrigerant into the evaporator based on temperature sensed at the outlet and the pressure inside the evaporator, keeping “superheat” in the sweet spot. That means cold air without icing up, stable cabin temps in Aussie and Kiwi summers, and decent performance even at idle. On the 1989 Pajero, the valve sits at the evaporator inlet, usually behind the glovebox where the A/C pipes pass through the firewall.

While it’s not a routine replacement item, a tired or contaminated TX‑valve can cause weak cooling, evaporator freeze‑ups, compressor short‑cycling, or odd gauge readings (very low suction with normal head, or hunting). If the system’s been open to atmosphere or a compressor has let go, the valve can gum up with debris or moisture. Whenever the system is opened, a new receiver‑drier, fresh O‑rings, correct oil, a thorough vacuum, and an accurate weighed charge are must‑dos.

Swapping the TX‑valve on a Pajero is mostly a dash‑side job. Expect to remove the glovebox, access the evaporator case, crack the lines, and unbolt the valve. Fit new O‑rings lubricated with the correct oil, position and insulate the sensing bulb properly on the outlet tube, and avoid overtightening fittings. If the vehicle has been converted from R12 to R134a, use compatible oil (ester for retrofits or the specified PAG for fully converted systems), replace the drier, and consider an R134a‑calibrated TX‑valve for best performance. Always recover refrigerant legally and have a licenced air‑con technician handle evacuation and charging. With a healthy TX‑valve and correct charge, the old Paj keeps its cool beautifully under the bonnet and in the bush.

• Common signs of a failing TX‑valve: poor cooling at idle, evaporator icing, rapid cycling, uneven vent temps.
• Best practice on replacement: new receiver‑drier, system flush if contaminated, evacuate to deep vacuum, weigh in charge, leak‑test.

Popular questions

Where is the TX‑valve on a 1989 Pajero?
It’s mounted at the evaporator inlet, typically behind the glovebox. You’ll see it where the A/C lines come through the firewall and connect to the evaporator core. Access usually means removing the glovebox and opening the evaporator housing.

What are the symptoms of a bad TX‑valve on this model?
Expect weak or inconsistent cooling, the evaporator icing up, odd pressure readings, or the compressor cycling too quickly. After a compressor failure or prolonged moisture ingress, the valve can stick or clog, so performance drops off noticeably.

Can the original R12 TX‑valve be used with R134a?
Many Pajeros run acceptably with the original valve after a proper retrofit (oil, drier, seals, and correct R134a charge). For best results, especially in hotter climates, a TX‑valve calibrated for R134a is recommended to sharpen low‑speed and high‑load cooling.