AC Receiver/Drier

This procedure covers the removal and replacement of the AC receiver/drier on a 2007-2013 Mercedes-Benz S65 AMG with the 6.0L V12 BiTurbo M275 engine, including refrigerant recovery, line disconnection, and system recharge.

Warnings

Tools required

Parts

• AC receiver/drier assembly × 1 — Use OEM specification
• AC line O-rings (assorted sizes) × 1 — Use OEM specification
• R134a refrigerant × 1 — Use OEM specification
• PAG 46 compressor oil × 1 — Use OEM specification

Preparation

1. Park vehicle on level surface and engage parking brake
2. Allow engine to cool completely if recently operated
3. Verify AC system refrigerant type is R134a (label on radiator support or hood)
4. Position refrigerant recovery machine and connect to AC service ports
5. Ensure recovery machine tank has adequate capacity and is certified for automotive use

Procedure

1. 1

   Recover AC refrigerant
   Connect AC recovery machine to low and high-side service ports. Follow recovery machine instructions to completely evacuate refrigerant from the system. Record the amount of refrigerant and oil recovered for recharge reference. Wait until machine indicates recovery is complete and system pressure is at 0 PSI.
   ⚠️Venting refrigerant to atmosphere is illegal and environmentally harmful. Always use certified recovery equipment.
2. 2

   Access receiver/drier location
   On the S65 AMG, the receiver/drier is mounted on the right side of the engine compartment near the condenser and radiator assembly. Remove the plastic engine cover by lifting upward on the front tabs. You may need to remove the right-side air intake ducting for better access. The receiver/drier is a cylindrical canister mounted vertically with the inlet from the condenser at the top and outlet to the evaporator at the bottom.
3. 3

   Disconnect AC line fittings
   Using appropriate line disconnect tools or wrenches, carefully disconnect the inlet line (from condenser) and outlet line (to evaporator) from the receiver/drier. Hold the receiver/drier body stationary while loosening the fittings to prevent twisting the assembly. Cap or plug all open fittings immediately to prevent moisture and contaminant entry. Place a drip pan underneath to catch any residual oil.
   ⚠Some residual refrigerant or oil may escape when lines are disconnected. Ensure area is well-ventilated.
   Torque spec

   AC Line Fittings20 Nm (15 lb-ft)
4. 4

   Remove mounting bolts
   Locate the mounting bracket that secures the receiver/drier to the body or radiator support. Remove the mounting bolts using a 10mm socket. The receiver/drier is typically held by 2-3 bolts on the mounting bracket. Support the receiver/drier while removing the final bolt.
   Torque spec

   Receiver Drier Bolts10 Nm (7 lb-ft)
5. 5

   Remove receiver/drier assembly
   Carefully lift the receiver/drier assembly out of the mounting bracket. Inspect the mounting bracket and surrounding area for corrosion, damage, or debris. Clean the mounting surfaces if necessary. Measure and record the amount of oil drained from the old receiver/drier by inverting it into a graduated container.
6. 6

   Prepare new receiver/drier
   Remove the new receiver/drier from its sealed packaging immediately before installation. Check that it includes new O-rings for the inlet and outlet fittings. Add the appropriate amount of fresh PAG 46 oil to the new receiver/drier based on the amount recovered from the old unit (typically 30-50ml). If no oil was recovered, add 30ml as a baseline.
7. 7

   Install O-rings and lubricate fittings
   Install new O-rings on both the inlet and outlet ports of the new receiver/drier. Lightly coat each O-ring with fresh PAG 46 oil to ensure proper sealing and prevent damage during installation. Inspect the AC line fittings for damage or worn O-rings and replace as needed.
   ⚠Never reuse old O-rings. Dried or damaged O-rings will cause refrigerant leaks.
8. 8

   Install receiver/drier assembly
   Position the new receiver/drier into the mounting bracket, ensuring proper orientation with inlet at top and outlet at bottom. Align the mounting holes and hand-thread the mounting bolts. Torque the mounting bolts to specification in a cross-pattern if multiple bolts are present.
   Torque spec

   Receiver Drier Bolts10 Nm (7 lb-ft)
9. 9

   Reconnect AC line fittings
   Remove caps or plugs from the AC lines and receiver/drier ports. Carefully align and hand-thread the inlet and outlet line fittings to the receiver/drier. Hold the receiver/drier body stationary while tightening. Torque both fittings to specification using a torque wrench.
   Torque spec

   AC Line Fittings20 Nm (15 lb-ft)
10. 10

    Evacuate AC system
    Connect the vacuum pump to the AC service ports using the manifold gauge set. Open the low and high-side valves and run the vacuum pump for a minimum of 45 minutes to remove all air and moisture from the system. The system should achieve and hold a vacuum of at least 29 inches Hg. After evacuation, close the valves and monitor for 10 minutes; vacuum should not drop more than 2 inches Hg, indicating no leaks.
    ⚠Inadequate evacuation will leave moisture in the system, which can freeze at the expansion valve and damage components.
11. 11

    Recharge AC system
    Using the recovery machine's recorded refrigerant amount or the vehicle specification (typically 1050-1150 grams for this model), recharge the system with R134a refrigerant. Charge through the low-side port with the engine running and AC on maximum cold. Monitor pressures on the manifold gauges. Low side should be 25-35 PSI and high side should be 200-250 PSI at ambient temperature of 75-85°F.
    ⚠Overcharging the system can cause compressor damage and poor cooling performance. Use a gram scale for accurate measurement.
12. 12

    Leak test system
    With the system fully charged, use an electronic leak detector or UV dye (if previously added) to check all connections at the receiver/drier and surrounding fittings for leaks. Pay special attention to the inlet and outlet connections. Check manifold gauge readings for stability. Any pressure drop indicates a leak that must be corrected.

Reassembly

1. Reinstall any air intake ducting or covers removed for access
2. Reinstall engine cover by aligning rear tabs first, then pressing down on front tabs until they click
3. Verify all tools and materials are removed from engine compartment

Verification

• Start engine and turn AC to maximum cold with blower on high
• Allow system to run for 10 minutes and verify cold air output from vents (typically 40-50°F at vents)
• Monitor AC system pressures: low side should be 25-35 PSI, high side 200-250 PSI at normal operating temperature
• Listen for unusual noises from the compressor or expansion valve area
• Verify no refrigerant odor or visible oil residue at receiver/drier connections
• Test AC performance under load by taking a test drive; cooling should remain consistent
• Recheck all connection points for leaks after 24 hours of operation

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