AC Compressor Clutch

Replace the AC compressor clutch assembly on a 2009 Aston Martin DB9, including refrigerant recovery, compressor removal, clutch replacement, and system recharge.

Warnings

Tools required

Parts

• AC compressor clutch assembly × 1 — Use OEM specification
• Compressor shaft seal and o-ring kit × 1 — Use OEM specification
• PAG 46 compressor oil × 1 — Use OEM specification
• Serpentine belt × 1 — Replace if worn or damaged

Fluids

• R-134a refrigerant

Preparation

1. Park vehicle on level surface and engage parking brake
2. Allow engine to cool completely for minimum 2 hours
3. Disconnect battery negative terminal located in trunk and wait 10 minutes
4. Raise vehicle on lift or support securely on jack stands at front lift points
5. Remove front undertray panels by removing Torx fasteners around perimeter
6. Have AC system professionally evacuated and refrigerant recovered into approved machine, recording total refrigerant weight removed

Procedure

1. 1

   Remove serpentine belt
   Locate the serpentine belt tensioner on the accessory drive (verify exact location per OEM service documentation). Insert the appropriate serpentine belt tool or breaker bar into the tensioner release point (verify tensioner type and drive size per DB9 OEM documentation). Rotate the tensioner in the direction that relieves tension (verify against the belt routing diagram) and slide belt off compressor pulley first, then remaining pulleys. Inspect belt for cracks, glazing, or fraying and replace if any wear is present. Note: Locate the serpentine belt tensioner. Insert 1/2-inch breaker bar or serpentine belt tool into the tensioner square drive. Rotate the tensioner in the direction required to relieve belt tension (verify direction against the DB9 belt routing/tensioner layout), then slide the belt off the compressor pulley first, followed by the remaining pulleys. Note: Rotate the tensioner in the direction that relieves belt tension (verify rotation direction against the belt routing diagram/service manual) and slide the belt off the compressor pulley first, then the remaining pulleys. Note: Locate the serpentine/accessory drive belt tensioner on the front of the engine (verify exact side and position against Aston Martin DB9 service documentation). Note: Accessory drive belt (verify single serpentine vs. multiple belts per DB9 OEM documentation)
2. 2

   Disconnect compressor electrical connector
   Locate the compressor clutch electrical connector on the front of the compressor housing. Press the locking tab and pull connector straight off the clutch coil terminals. Secure connector away from work area to prevent damage.
3. 3

   Disconnect AC line fittings
   Locate the high-side and low-side AC line connections at the compressor (often a bolted manifold block). Remove the manifold retaining bolt or line fittings as applicable using the appropriate tool, and separate the lines from the compressor. Immediately cap all open ports with rubber plugs to prevent moisture and debris entry. Inspect o-rings for damage and discard them. Note: Locate the AC manifold connection on the compressor (often a single bolted manifold block with high-side and low-side ports). Remove the manifold retaining bolt (or loosen line fittings as applicable), separate the lines from the compressor, and immediately cap all open ports with rubber plugs to prevent moisture and debris entry. Inspect O-rings for damage and discard them. Note: Locate the high-side and low-side AC line connections at the compressor. Depending on the fitting type (flare-nut or block/manifold with retaining bolt), use the appropriate tool to loosen and remove the connections (verify fitting type against service documentation). Note: Compressor PAG oil (verify correct PAG viscosity grade per DB9 OEM specification)
4. 4

   Remove compressor mounting bolts
   Locate the compressor mounting bolts securing the compressor to the engine bracket. Remove the compressor mounting bolts (verify exact count and location against DB9 service data) using an appropriate socket. Support compressor weight while removing final bolt. Carefully lower compressor from engine bay and place on clean work surface. Note: Remove the compressor mounting bolts (verify exact count per OEM documentation) using the appropriate socket. Note: Remove the compressor mounting bolts using the appropriate socket (verify exact count and location against Aston Martin DB9 service documentation).
   Torque spec

   Compressor Bolts25 Nm (18 lb-ft)
5. 5

   Remove clutch pulley snap ring
   Inspect compressor shaft and clutch assembly. Locate the large snap ring retaining the clutch pulley and bearing assembly on the compressor shaft. Using snap ring pliers, carefully expand and remove the snap ring. Keep snap ring clean and inspect for damage or distortion.
6. 6

   Remove clutch pulley and bearing assembly
   With snap ring removed, carefully pull the clutch pulley and bearing assembly straight off the compressor shaft. This may require gentle rocking motion. Inspect bearing for roughness, noise, or resistance when spinning by hand. Set assembly aside on clean surface.
7. 7

   Remove clutch plate
   Locate the clutch friction plate on the compressor shaft, retained by a center bolt or snap ring. If bolt-retained, use clutch holding tool or carefully hold the plate while loosening the center retaining bolt. Remove clutch plate from shaft and inspect for wear, glazing, or oil contamination on friction surfaces.
8. 8

   Remove electromagnetic coil assembly
   Locate the retaining screws or snap ring securing the electromagnetic coil assembly to the compressor nose. Remove fasteners and carefully pull coil assembly off compressor housing. Inspect coil windings and connector terminals for damage, corrosion, or burning. Measure coil resistance with a multimeter and compare against the OEM clutch coil resistance specification for the 2009 DB9 (verify value in service data) before determining serviceability. Note: Measure coil resistance with a multimeter and compare to the OEM specification for this compressor's clutch coil. Note: Measure coil resistance with a multimeter and compare to the specification for this compressor's clutch coil (verify exact resistance value against manufacturer documentation).
9. 9

   Inspect and replace shaft seal
   With clutch components removed, inspect the compressor shaft seal at the nose of the housing. If any refrigerant oil leakage is visible or seal shows damage, use seal removal tool to extract old seal and O-ring. Clean shaft and seal bore thoroughly. Install new seal from kit using seal installer, ensuring it seats flush. Apply thin coat of refrigerant oil to seal lip.
10. 10

    Install new electromagnetic coil
    Position new or cleaned electromagnetic coil assembly onto compressor nose, aligning mounting holes. Install retaining screws or snap ring and tighten fasteners evenly. Verify coil sits flush against housing with no gaps. Route electrical connector for easy access during installation.
11. 11

    Install new clutch plate
    Install new clutch friction plate onto compressor shaft with friction surface facing outward toward pulley. If bolt-retained, apply thread-locking compound to center bolt threads (if specified) and torque to the DB9 OEM specification (verify exact value in service data — do not use an assumed value) using a holding tool. If snap ring retained, install snap ring ensuring it fully seats in shaft groove. Verify clutch plate air gap from pulley surface meets the OEM specification when measured with a feeler gauge. Note: If bolt-retained, apply thread-locking compound only if specified by OEM, then torque the center bolt to the DB9 OEM specification (verify exact value in service data) using a holding tool. Note: Verify the clutch plate air gap matches the OEM specification for the DB9 compressor clutch (verify exact value in service data) when measured with a feeler gauge. Note: Verify the clutch plate air gap from the pulley surface matches the manufacturer specification (typically in the 0.3-0.6mm range) using a feeler gauge (verify exact value against compressor documentation). Note: If bolt-retained, apply thread-locking compound to the center bolt threads (if specified) and torque to the manufacturer specification using a holding tool (verify exact torque value against documentation).
12. 12

    Install pulley and bearing assembly
    Slide new or inspected pulley and bearing assembly onto compressor shaft, ensuring it slides smoothly over clutch plate. Align snap ring groove and install retaining snap ring using snap ring pliers. Verify snap ring is fully seated in groove around entire circumference. Spin pulley by hand to verify smooth rotation without binding.
13. 13

    Add compressor oil
    With compressor horizontal on work surface, remove oil fill plug from compressor housing. Drain old oil into graduated container and measure quantity. Add new PAG oil of the viscosity specified by the OEM (verify PAG grade for this compressor) matching the amount drained plus any additional oil specified by the new clutch installation instructions. Reinstall fill plug and tighten securely. Note: Add new PAG oil of the correct viscosity for this compressor (verify PAG grade against Aston Martin/compressor specification), matching the amount drained plus any additional oil specified by the new clutch installation instructions.
14. 14

    Install compressor to engine
    Position compressor onto engine mounting bracket, aligning all mounting bolt holes. Install the mounting bolts hand-tight (verify exact count and location per DB9 OEM service data), then torque in cross pattern to specification. Verify compressor sits flush against bracket with no gaps.
    Torque spec

    Compressor Bolts25 Nm (18 lb-ft)
15. 15

    Reconnect AC lines and electrical
    Install new O-rings onto AC line fittings, lubricating with refrigerant oil. Reconnect the AC lines to the compressor (manifold block or individual fittings as applicable) and tighten the manifold bolt or fittings to the DB9 OEM torque specification (verify exact value in service data — do not rely on assumed values). Connect clutch electrical connector, ensuring locking tab clicks into place. Tug gently to verify secure connection. Note: Reconnect the high-side and low-side lines to the compressor (manifold block or fittings as applicable) and tighten to the OEM torque specification. Note: Reconnect the high-side and low-side AC line connections using the appropriate tool for the fitting type, and tighten to the manufacturer torque specification (verify exact torque values against documentation).
16. 16

    Install serpentine belt
    Route serpentine belt around all pulleys except compressor pulley according to belt routing diagram on radiator support. Rotate the tensioner in the tension-relieving direction with a breaker bar and slide the belt onto the compressor pulley last. Release tensioner slowly and verify belt is properly seated in all pulley grooves with no twists.
17. 17

    Vacuum and recharge AC system
    Connect AC service machine to high and low side service ports. Pull vacuum on system for minimum 45 minutes to remove all moisture and air. Monitor vacuum gauge for 15 minutes after pump stops; vacuum should hold indicating no leaks. Recharge the system to the OEM-specified R-134a refrigerant capacity for the 2009 DB9 (verify exact charge weight in service data; do not rely solely on the recovered amount). Add UV dye if desired for future leak detection.

Reassembly

1. Reinstall front undertray panels with all Torx fasteners
2. Lower vehicle from lift or jack stands
3. Reconnect battery negative terminal in trunk
4. Start engine and immediately verify no unusual noises from compressor area

Verification

• Start engine and set AC to maximum cold with blower on high
• Verify compressor clutch engages with audible click when AC is turned on
• Confirm cold air output from vents reaches approximately 40-45°F within 3-5 minutes
• Inspect all AC line fittings and compressor seals for refrigerant oil leakage
• Verify serpentine belt tracks properly in all pulley grooves with no slipping or noise
• Use UV light to inspect for any refrigerant leaks if dye was added
• Check compressor clutch air gap is within 0.4-0.6mm specification using feeler gauge
• Monitor AC performance over several drive cycles to ensure consistent operation

Related trouble codes on this vehicle

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