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Here is the pattern on these cars: the A/C cools on the highway, drifts warm in town, then quits. The quote that follows is a compressor at over $540 from a Mitsubishi parts counter. Run the checks below before paying.

When the verdict lands on the compressor, the part is the A/C compressor for the 2008-2009 Lancer and Outlander, catalogued under the shortened 7813A32 rendering of 7813A328. It ships with the clutch for $160.46.

Warm air from the vents: three failures, one symptom

Low refrigerant is the most common cause of warm vents here, not a dead pump. The refrigerant carries the compressor's oil, so a slow leak starves both.

Three failures all show up as warm air. Sort them cheapest first:

• Low charge: a leak upstream — a shaft seal, a stone-damaged condenser, or an O-ring. A pressure switch (a small sensor that cuts clutch power at low pressure) then keeps the pump off.
• Tired pump: this swash-plate design (an inclined plate converting spin into piston strokes) seals worse after high mileage. Vents climb at idle but recover at speed.
• Airflow: a bug-packed condenser or a dead fan raises hot-side pressure until the switch cuts the clutch. Hosing the condenser rules this out.

The clutch that will not pull in

A clutch that never engages is an electrical problem until proven otherwise. The chain runs from the A/C fuse through the relay and pressure switch to the coil.

• Check for battery voltage at the compressor's two-pin connector with the A/C on.
• Voltage present clears the fuse, relay, and switch — the clutch is now the suspect.
• No voltage means the fault is upstream — find it before ordering anything.

Voltage present but the clutch hanging off? Measure the coil. A healthy 12-volt coil reads 3-5 Ω; an open circuit convicts it, and a near-short means a cooked winding.

If the coil measures fine, inspect the air gap — the tiny space between plate and pulley face. Wear or rust there stops the plate from pulling in.

This lockout logic plays out everywhere. Our PXC14 compressor guide for the 2016-2018 Chevrolet Cruze walks the same checks on a GM car. The rule never changes: no compressor on symptoms alone.

One compressor, a family of numbers

Every number in that table buys the same pump and clutch. What separates boxes is the included clutch, the shipped oil, and the warranty.

Genuine units run roughly $545 to $805 at the counter — which is why the $160.46 aftermarket version is where most owners land.

Not every 95 mm Mitsubishi clutch is this compressor

Mitsubishi used visually similar six-groove, 95 mm-clutch units across several platforms. Only catalogue numbers separate them. Check before you order.

• Previous generation: the 10350931 compressor for the 2004-2006 Lancer and 2003-2006 Outlander is a different pump with different ports, at $126.11, and does not interchange.
• Galant family: the ECCPP compressor for the 2006-2012 Galant, Endeavor, and Eclipse is an MSC105 unit — six grooves, 95 mm, PAG 46 — and none of its OE numbers (255603, 275601, 77493, TEM variants) fits your car.

Match the model code to the OE number on your old housing: MSC90CAS here, MSC105 for the Galant family. Both sit in the A/C and heating parts collection.

What the replacement actually involves

The compressor sits low on the front of the 4B11 and 6B31. Walk-throughs measure the job in hours, not days:

1. Recover the refrigerant with a machine.
2. Unplug the clutch connector.
3. Remove the two line bolts at the back of the pump.
4. Unbolt the mounting lugs and lift the unit out.
5. Fit new O-rings and torque both line joints to spec.
6. Replace the receiver-drier, pull a deep vacuum, then weigh in the charge.

Front-of-engine access is shared across the generation. The timing belt and water pump guide for the 2004-2009 Lancer and Eclipse covers the same teardown — combine jobs if the belt is due.

The caution in owner accounts is physical. The condenser and radiator sit in the working area, and a slipped wrench turns a $160 repair into a two-core repair.

The work that keeps the new pump alive

Replace the receiver-drier every time. It is a small canister that dries moisture out of the refrigerant — the one part you cannot flush.

After an internal failure the drier is also full of debris, and guides call for inspecting the expansion valve too. If the old pump shed metal, flush the condenser and lines and blow the evaporator out both ways. Skipping the drier to save $30 is why fresh compressors come back within a season.

Oil and charge: two numbers off the label

Total oil capacity is about 70 cc (2.4 fl oz) of PAG oil. Measure what ships in the new compressor first, then split the rest between pump and drier.

• Refrigerant: 500 g of R-134a, tolerance 20 g — about 16-18 ounces per the NRF chart.
• Vacuum: at least thirty minutes, to boil moisture out first.
• Authority: your car's under-hood label wins over any chart.

Weighing the charge instead of guessing by can is standard R-134a practice. Our compressor buyer's guide for the 1998-2000 Subaru Forester and 1993-2001 Impreza explains why.

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