Parts for your 1999 Mitsubishi Pajero-Tx valve

1999 Mitsubishi Pajero TX-Valve: What It Does and When to Replace It

Based on factory documentation and parts catalogues, the 1999 Mitsubishi Pajero is fitted with a thermal expansion valve (TX-valve) in its air-conditioning system, not a fixed orifice tube. This is confirmed by Mitsubishi’s workshop manual coverage for the V2/V4 series Heater & Air Conditioner Group (Group 55: Expansion Valve), Mitsubishi ASA parts listings for the Pajero up to 1999 (common valve part numbers include MB913066/MR141708), and general AC system references from DENSO’s automotive air-conditioning service guides. So, yes—TX-valve is relevant and used on the 1999 Pajero.

On this model, the TX-valve meters refrigerant into the evaporator based on temperature and pressure, keeping the evaporator cold without letting it freeze. It’s the control gate that balances efficiency and comfort: too little flow and the cabin never cools properly, too much and the system can flood, causing poor cooling and potential compressor grief. The Pajero’s TX-valve is typically mounted at, or just outside, the evaporator core in the HVAC case.

When servicing a 1999 Pajero’s air-con, the TX-valve deserves a look if there’s weak cooling, fluctuating vent temps, frost on lines, or high/low side pressures that don’t behave as expected. Because the valve sits within the sealed refrigerant circuit, any replacement should be done by an AC-certified technician with proper recovery gear.

• Common symptoms of a crook TX-valve:
  • Slow or no cool-down, especially at idle
  • Icing on the evaporator or suction line
  • Hunting vent temperatures and noisy hiss at the firewall
  • Pressure readings showing low low-side and high high-side (stuck closed), or the reverse (stuck open)

1. Diagnosis first: verify charge level, condenser airflow, and compressor operation before blaming the valve.
2. If the valve’s suspect, evacuate the system, remove the HVAC case access panel, and replace the TX-valve with new O-rings.
3. Always replace the receiver-drier/accumulator when opening the system, then vacuum to deep levels and re-gas to the specified charge.
4. After refit, check for leaks and confirm stable pressures and vent temps.

There’s no regular “maintenance” on the TX-valve itself, but keeping the system clean and dry is crucial—moisture and debris are what usually make a valve stick. If the Pajero’s air-con is original or the system’s been open, a proactive drier change and a careful inspection of the TX-valve can save later headaches.

Popular questions about 1999 Mitsubishi Pajero TX-valve

Where is the TX-valve located on a 1999 Pajero?
It’s mounted at the evaporator inlet within the HVAC case, typically accessed from the passenger side behind the dash or via a service panel near the firewall. Expect to remove trim or parts of the glovebox area to reach it.

Do I need to re-gas after replacing the TX-valve?
Yes. The system must be evacuated, the valve swapped with new O-rings, then vacuumed and recharged to the factory specification. Skipping the vacuum step risks moisture in the system and poor cooling performance.

What are the signs my TX-valve is failing?
Weak cooling, temperature swings at the vents, frost on lines, and odd pressure readings during gauge testing are classic signs. Rule out low refrigerant and condenser airflow issues first.