🔧 Forester - A/C Compressor Replacement

Replacing the A/C compressor means safely recovering the refrigerant, removing the drive belt and A/C lines, swapping the compressor, then pulling a deep vacuum and recharging the system to the correct amount. This is critical because opening the A/C system lets moisture in, which can quickly damage the new compressor if the system isn’t evacuated properly.

Difficulty Level: Advanced | Estimated Time: 3-6 hours

Assumption: common Subaru FA20 A/C specs used; verify if available.

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⚠️ Safety & Precautions

• ⚠️ Refrigerant must be recovered—do not vent to air (illegal and dangerous).
• ⚠️ Wear safety glasses and gloves; liquid refrigerant can cause frostbite.
• ⚠️ Work on a cool engine; keep hands clear of the belt path.
• ⚠️ Disconnect the negative battery terminal before unplugging compressor wiring.
• ⚠️ Cap open A/C lines immediately to keep moisture/dirt out.

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🔧 Required Tools

You'll need the following tools for this repair:

• Safety glasses
• Nitrile gloves
• Floor jack (rated 3-ton minimum)
• Jack stands (rated 3-ton minimum)
• Wheel chocks
• 10mm socket
• 12mm socket
• 14mm socket
• 3/8" ratchet
• 3/8" torque wrench (10–80 ft-lbs range)
• 6" extension (3/8")
• Trim clip removal tool
• Flat-blade screwdriver
• Line caps/plugs assortment
• Manifold gauge set for R-134a (specialty)
• Vacuum pump (specialty)
• Refrigerant scale (specialty)
• Refrigerant recovery machine (specialty)

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• A/C compressor - Qty: 1
• A/C compressor O-ring set - Qty: 1
• PAG A/C oil (Subaru/Denso SP-10 equivalent) - Qty: 1
• R-134a refrigerant - Qty: 1 (enough for full charge)

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📋 Before You Begin

• Park on level ground, set the parking brake, and chock the rear wheels.
• Plan A/C service: have a shop recover the refrigerant first, or use a refrigerant recovery machine (it pulls refrigerant out safely into a tank).
• Disconnect the battery: use a 10mm socket to remove the negative terminal and isolate it.
• Raise the front and support it: use a floor jack and jack stands under the proper front support points.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Recover the refrigerant

• Use a refrigerant recovery machine (specialty) to fully recover the system.
• If you don’t have recovery equipment, have a shop recover it before you start disassembly.
• Never loosen A/C lines under pressure.

Step 2: Remove the lower engine cover (undertray)

• Use a trim clip removal tool and 10mm socket to remove the clips/bolts holding the undertray.
• Set hardware aside in a small container so nothing gets lost.

Step 3: Remove the accessory drive belt

• Locate the belt tensioner.
• Use a 14mm socket and 3/8" ratchet on the tensioner to relieve belt tension, then slip the belt off the compressor pulley.
• Take a quick photo of belt routing.

Step 4: Unplug the compressor electrical connector

• Use a flat-blade screwdriver gently to release the connector lock if needed.
• Pull the connector straight off—don’t tug on the wires.

Step 5: Remove the A/C lines from the compressor

• Clean around the fittings first to keep dirt out.
• Use a 10mm socket (typical) to remove the line retaining bolt(s) at the compressor manifold block.
• Carefully wiggle the lines free; expect a small hiss only if recovery was incomplete.
• Immediately install line caps/plugs assortment on both the lines and the compressor ports.
• Torque to 9.8 Nm (7.2 ft-lbs) for the line retaining bolt(s).

Step 6: Remove the compressor mounting bolts and compressor

• Support the compressor with one hand before removing the last bolt.
• Use a 12mm socket and 3/8" ratchet with a 6" extension to remove the compressor mounting bolts.
• Lower the compressor out from underneath.
• Torque to 25 Nm (18 ft-lbs) for compressor mounting bolts.

Step 7: Prepare the new compressor (oil balancing)

• Drain and measure oil from the old compressor into a clean container (tilt and rotate the hub by hand).
• Add the same amount of new PAG A/C oil (Subaru/Denso SP-10 equivalent) into the new compressor.
• Rotate the compressor hub by hand 10–15 turns to distribute oil.
• Too much oil reduces cooling performance.

Step 8: Replace O-rings and install the new compressor

• Remove old O-rings from the A/C line ends.
• Lightly coat new O-rings with clean PAG A/C oil and install them.
• Position the compressor and start all mounting bolts by hand (prevents cross-threading).
• Use a 12mm socket to snug, then use a 3/8" torque wrench.
• Torque to 25 Nm (18 ft-lbs) for compressor mounting bolts.

Step 9: Reinstall the A/C lines

• Remove the caps/plugs right before assembly.
• Seat the line block squarely (do not force it).
• Use a 10mm socket to install the retaining bolt(s).
• Torque to 9.8 Nm (7.2 ft-lbs) for the line retaining bolt(s).

Step 10: Reconnect wiring and reinstall the drive belt

• Plug the compressor connector back in until it clicks.
• Route the belt correctly, then use a 14mm socket to relieve tension and slip the belt back on.
• Visually confirm the belt is fully seated in every pulley groove.

Step 11: Reinstall the undertray and lower the vehicle

• Reinstall the undertray using a 10mm socket and trim clip removal tool.
• Lower the vehicle from the jack stands using the floor jack.

Step 12: Evacuate (vacuum) and recharge the A/C system

• Connect the manifold gauge set for R-134a (specialty) and a vacuum pump (specialty).
• Pull vacuum for 30–45 minutes, then close valves and verify it holds vacuum for 10–15 minutes (leak check).
• Recharge by weight using a refrigerant scale (specialty).
• Charge amount (common): 0.48 kg (1.06 lb / 16.9 oz) R-134a

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✅ After Repair

• Reconnect the battery negative terminal using a 10mm socket.
• Start the engine and set HVAC to MAX A/C, recirculation ON, blower medium-high.
• Confirm the compressor engages, air gets cold, and there are no unusual noises.
• Check for leaks at the compressor line block (oily residue is a clue).
• If cooling is weak, charge weight may be off.

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💰 DIY vs Shop Cost

Shop Cost: $900-$1,800 (parts + labor)

DIY Cost: $350-$950 (parts only)

You Save: $550-$850 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 2.5-4.0 hours.

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🎯 Ready to get started?

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