AC Compressor

Complete removal and replacement of the AC compressor on a 2009 Aston Martin DB9 6.0L V12, including refrigerant recovery, serpentine belt removal, and system recharge.

Warnings

Tools required

Parts

• AC Compressor × 1 — Use OEM specification or quality aftermarket equivalent
• AC line O-rings (high-side and low-side) × 1 — Use OEM specification
• Serpentine belt × 1 — Use OEM specification - recommend replacement at compressor change
• PAG 46 compressor oil × 1 — Use OEM-specified PAG viscosity
• R-134a refrigerant × 1 — R-134a

Fluids

• R-134a refrigerant

Preparation

1. Park vehicle on level surface and engage parking brake.
2. Allow engine to cool completely if recently run (minimum 2 hours).
3. Disconnect negative battery terminal to prevent accidental engine start.
4. Verify AC recovery machine is properly functioning and certified for R-134a.
5. Position vehicle lift or support vehicle securely on jack stands if underside access is needed for your specific approach angle.
6. Have new O-rings and PAG oil ready before opening AC system.

Procedure

1. 1

   Recover AC refrigerant
   Connect AC recovery machine to the high-side and low-side service ports. Follow recovery machine instructions to fully evacuate the AC system. Document the amount of refrigerant and oil recovered for recharge reference. Wait until recovery machine indicates system is at vacuum and all refrigerant has been removed. This process typically takes 15-30 minutes depending on system charge level.
2. 2

   Remove engine cover and locate compressor
   Remove the engine cover by releasing the quick-release fasteners or Torx fasteners securing it. The AC compressor is located at the front of the engine, driven by the accessory drive belt. Confirm exact location per OEM documentation. Identify the compressor, its electrical connector, and the high-side and low-side refrigerant lines (confirm which is which per OEM documentation for this vehicle). Confirm whether the compressor uses a clutch or a control valve per OEM documentation.
3. 3

   Disconnect compressor clutch connector
   Locate the electrical connector on the compressor clutch assembly. Depress the locking tab and disconnect the electrical connector from the compressor. Secure the connector away from the work area to prevent damage.
   Torque spec

   Clutch Connector Bolt8 Nm (6 lb-ft)
4. 4

   Remove serpentine belt
   Locate the belt tensioner on the front of the engine. Using a serpentine belt tool or 1/2" breaker bar, rotate the tensioner in the direction that relieves belt tension (confirm direction for this engine) to loosen the belt. Slide the belt off one pulley, then slowly release tensioner pressure. Remove the belt from all pulleys and extract from engine bay. Inspect belt for wear; if glazed, cracked, or contaminated with oil, replace with new belt during reassembly. Note: Rotate the tensioner in the direction that relieves belt tension (confirm direction for this engine per OEM documentation) using a serpentine belt tool or breaker bar, then slip the belt onto the final pulley.
5. 5

   Disconnect AC refrigerant lines
   Position a catch container beneath the compressor to collect residual refrigerant oil. Using appropriate wrench size, loosen and remove the high-side line fitting bolt from the compressor rear. Remove the fitting and immediately cap the open line to prevent contamination. Repeat for the low-side line fitting. Remove and discard the old O-rings from both fittings. Inspect line fitting seats for damage or debris.
   Torque spec

   AC Line Fittings20 Nm (15 lb-ft)
6. 6

   Remove compressor mounting bolts
   Locate the compressor mounting bolts securing the compressor to the engine block mounting bracket (confirm exact number and locations per OEM documentation for this vehicle). These are typically accessed from the front and side of the compressor. Remove all mounting bolts completely and set aside. Support the compressor weight as you remove the final bolt.
   Torque spec

   AC Compressor Bolts25 Nm (18 lb-ft)
7. 7

   Extract compressor from engine bay
   Carefully maneuver the compressor away from the mounting bracket, navigating around surrounding components. The compressor may require tilting or rotation to clear hoses, wiring harnesses, and structural components. Lift the compressor out of the engine bay and place on a clean work surface. Drain any residual oil from the old compressor into a graduated container and measure the amount for reference.
8. 8

   Prepare new compressor
   Remove shipping plugs or caps from the new compressor ports. Check the new compressor oil level according to manufacturer specifications. Measure the oil drained from the old compressor and balance the new compressor oil charge to match the OEM-specified total system oil capacity for this vehicle. If old compressor oil was contaminated or you recovered an abnormal amount, consult AC system flushing procedures before proceeding. Distribute oil in the new compressor per OEM instructions, then rotate compressor pulley by hand several revolutions to distribute oil internally.o distribute oil internally. Note: PAG compressor oil (OEM-specified viscosity) Note: OEM-specified PAG compressor oil (confirm viscosity per OEM documentation)
9. 9

   Install new compressor
   Maneuver the new compressor into position in the engine bay, reversing the extraction path from step 7. Align the compressor mounting holes with the bracket on the engine block. Hand-thread all 3 mounting bolts to ensure proper alignment before tightening any bolt fully.
   Torque spec

   AC Compressor Bolts25 Nm (18 lb-ft)
10. 10

    Torque compressor mounting bolts
    Using a calibrated torque wrench, tighten the compressor mounting bolts to the manufacturer-specified torque in a cross/alternating pattern to ensure even clamping force. Verify all bolts are seated properly and compressor is secure with no movement.
    Torque spec

    AC Compressor Bolts25 Nm (18 lb-ft)
11. 11

    Install new O-rings and reconnect AC lines
    Lubricate new O-rings with clean PAG oil and install them onto both high-side and low-side line fittings. Ensure O-rings are properly seated in their grooves without twisting. Connect the high-side line to the compressor rear port and hand-thread the fitting bolt. Repeat for the low-side line. Using a torque wrench, tighten both line fittings to the manufacturer-specified torque. Do not over-tighten as this can damage the O-rings or aluminum fittings.
    Torque spec

    AC Line Fittings20 Nm (15 lb-ft)
12. 12

    Reinstall serpentine belt
    Route the serpentine belt around all pulleys according to the belt routing diagram (typically found on a decal in the engine bay or in the owner's manual). Ensure the belt ribs are properly seated in all pulley grooves. Rotate the tensioner clockwise using a serpentine belt tool or breaker bar, then slip the belt onto the final pulley. Slowly release tensioner pressure to apply proper belt tension. Verify the belt is correctly seated on all pulleys with no misalignment.
13. 13

    Reconnect electrical connector
    Connect the electrical connector to the compressor clutch assembly. Ensure the connector locks into place with an audible click. Gently tug on the connector to verify it is fully seated and secure.
14. 14

    Evacuate and recharge AC system
    Connect AC service machine to high-side and low-side service ports. Perform a complete system evacuation for a minimum of 30 minutes to remove all air and moisture. Monitor vacuum gauge; system should hold vacuum without loss for at least 10 minutes, indicating no leaks. If vacuum holds, recharge the system with the documented amount of R-134a refrigerant recovered in step 1, or per manufacturer specifications if significantly different. Add UV dye if equipped or desired for future leak detection. Note: Check system pressures using AC manifold gauges and compare against OEM-specified low-side and high-side pressures for the given ambient temperature.
15. 15

    Reinstall engine cover and reconnect battery
    Reinstall the engine cover, securing all fasteners properly. Reconnect the negative battery terminal. Remove any tools or materials from the engine bay.

Reassembly

1. Ensure all AC line fittings are torqued to specification with new lubricated O-rings installed.
2. Verify serpentine belt is properly routed and seated on all pulleys before starting engine.
3. Confirm compressor clutch electrical connector is fully seated and locked.
4. Double-check all mounting bolts are torqued to 25.0 Nm and secure.

Verification

• Start engine and set AC to maximum cold with fan on high. Compressor clutch should engage within 10-30 seconds.
• Verify compressor is running smoothly without unusual noise, vibration, or belt squealing.
• Monitor AC vent temperature; should reach 40-50°F (4-10°C) within 5 minutes of operation.
• Inspect all AC line connections for signs of refrigerant leaks using electronic leak detector or soap solution.
• Check system pressures using AC manifold gauges: typical low-side 25-45 PSI, high-side 200-250 PSI at idle with ambient temperature 70-80°F.
• Verify no warning lights on instrument cluster related to AC system.
• Run AC system for 10-15 minutes and recheck all connections and compressor operation before returning vehicle to service.

Related trouble codes on this vehicle

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