AC Hose Assembly

Remove and replace the AC hose assembly on a 2009 Aston Martin DB9, including recovery and recharge of R-134a refrigerant and verification of system operation.

Warnings

Tools required

Parts

• AC hose assembly × 1 — Use OEM specification - varies by location (high/low pressure, evaporator/condenser)
• AC line O-ring kit × 1 — Use OEM specification for specific hose assembly
• PAG oil × 1 — PAG 46 or OEM equivalent

Fluids

• R-134a refrigerant

Preparation

1. Ensure engine is completely cold to touch
2. Position vehicle on lift or securely support on jack stands with level access to undercarriage and engine bay
3. Verify AC system has been off for at least 30 minutes to allow pressure equalization
4. Photograph hose routing and connection points before disassembly for reference during installation
5. Place fender covers to protect painted surfaces during work in engine bay

Procedure

1. 1

   Recover AC refrigerant
   Connect the recovery machine appropriate for the refrigerant type listed on the vehicle's underhood AC label (R-134a for 2009 DB9) to the AC service ports. Follow machine manufacturer procedures to fully recover all refrigerant from the system. Record the amount recovered for recharge reference. Allow system to stabilize at atmospheric pressure before disconnecting gauges. Allow the recovery machine to complete its cycle and confirm the system has reached a stable low pressure before disconnecting, indicating complete recovery. Note: Allow system to stabilize at atmospheric pressure before disconnecting gauges. Confirm the recovery machine indicates the system has reached the target low vacuum and no further refrigerant is being pulled, verifying complete recovery. Note: Allow the system to stabilize and confirm the recovery machine indicates the system has reached atmospheric/near-vacuum pressure before disconnecting, confirming all refrigerant has been recovered.
2. 2

   Access the hose assembly connections
   Remove the engine cover per the manufacturer's specified procedure, releasing the retaining fasteners or clips as applicable for the 2009 DB9 6.0L V12. For hoses routed along the firewall or lower engine bay, access may require removing the undertray. Remove undertray Torx fasteners and lower the panel. For hoses near the compressor, ensure clear access to mounting brackets and line fittings. Note: Remove the engine cover per the OEM service procedure, releasing any fasteners or clips as specified for the 2009 DB9 V12 before lifting the cover clear.
3. 3

   Disconnect upstream AC line fitting
   Clean the fitting connection area thoroughly with shop towels to prevent contamination. Using the appropriate AC line disconnect tool, release the spring-lock coupling or loosen the threaded fitting at the upstream connection point. For threaded fittings, support the component body with a backup wrench while loosening to prevent twisting the line. Allow residual oil to drain into the drain pan. Cap the open port immediately with a clean plug to prevent moisture and debris intrusion.
4. 4

   Disconnect downstream AC line fitting
   Repeat the disconnect procedure for the downstream connection point of the hose assembly. Support the component body with a backup wrench if using threaded fittings. Allow residual oil to drain and cap the open port immediately. Note the condition and position of any O-rings visible at the connections for comparison with new parts.
5. 5

   Release hose mounting brackets
   Locate the mounting brackets securing the hose assembly to the chassis or engine. Remove 2-3 Torx fasteners per bracket location (typically T25 or T30). Track bracket orientation and fastener locations for reinstallation. Some hoses may have rubber-isolated clips that can be released by hand after removing fasteners.
6. 6

   Remove hose assembly
   Carefully maneuver the hose assembly out of the engine bay, noting any tight clearances or routing through frame members. Avoid bending or kinking the hose during removal. If resistance is encountered, verify all brackets and fasteners have been removed. Inspect the removed hose for signs of abrasion, oil staining, or damage that may indicate the cause of failure.
7. 7

   Prepare new hose assembly
   Remove protective caps from the new hose assembly. Inspect the hose routing shape and confirm it matches the removed assembly. Install new O-rings at both connection points, lightly lubricating each O-ring with fresh PAG oil. Add 2-3 ml of PAG oil into each open port of the new hose to replace oil lost during the repair. Ensure O-rings are properly seated in their grooves without twisting or pinching.
8. 8

   Route new hose assembly
   Carefully route the new hose assembly through the engine bay following the exact path of the original. Reference photographs taken during disassembly. Ensure the hose does not contact sharp edges, hot exhaust components, or moving parts. Verify adequate clearance from the engine block, alternator, and accessory drive components. The hose should follow a natural curve without tension or kinking.
9. 9

   Install mounting brackets
   Position the hose assembly into its mounting brackets, ensuring proper alignment and no twisting of the hose. Install and hand-tighten the Torx fasteners to secure brackets to the chassis or engine. Verify the hose sits naturally in each bracket without binding. Tighten bracket fasteners to the Aston Martin OEM-specified torque in a pattern that maintains even hose support (verify specification before final tightening). Note: Tighten bracket fasteners to the manufacturer-specified torque (verify in Aston Martin workshop manual for the 2009 DB9) in a pattern that maintains even hose support. Note: Tighten bracket fasteners to the OEM-specified torque for the 2009 Aston Martin DB9 (verify value in factory service data) in a pattern that maintains even hose support.
10. 10

    Connect downstream AC line fitting
    Remove the protective cap from the downstream port. Verify the O-ring is properly positioned and lubricated. Align the fitting and push the spring-lock coupling fully home until it clicks, or hand-start threaded fittings carefully to avoid cross-threading. For threaded connections, use a backup wrench on the component body and tighten the line fitting to specification.
    Torque spec

    AC Line Fittings20 Nm (15 lb-ft)
11. 11

    Connect upstream AC line fitting
    Remove the protective cap from the upstream port. Verify the O-ring is properly positioned and lubricated. Align the fitting and connect using the same method as the downstream connection. Ensure spring-lock couplings are fully engaged or tighten threaded fittings to specification using a backup wrench.
    Torque spec

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

    Reinstall access panels
    Reinstall the undertray if removed, securing with Torx fasteners. Reinstall the engine cover by aligning the mounting grommets and pressing down firmly until it seats. Verify all panels are secure and properly aligned.
13. 13

    Evacuate and recharge AC system
    Connect the R-134a recovery/recharge machine to the service ports. Pull a vacuum on the system to at least 29 inHg (approximately 1000 microns / 29 inHg vacuum below atmospheric) and hold for 30-45 minutes to remove moisture and verify system integrity. If the vacuum does not hold, locate and repair the leak. Once vacuum test passes, recharge the system to the OEM total refrigerant capacity specified on the under-hood AC label or workshop manual for the 2009 DB9, and add PAG oil equal to the amount lost during the repair per the manufacturer specification. Follow machine procedures for accurate charging. Follow machine procedures for accurate charging. Note: recharge the system with the OEM-specified refrigerant charge for the 2009 DB9, accounting for the amount recovered, and top off PAG oil only to replace the quantity lost during the repair per OEM specification Note: Once vacuum test passes, recharge the system with the OEM-specified R-134a capacity for the 2009 Aston Martin DB9 (verify in factory service data), and add the OEM-specified amount of PAG oil to replace oil lost during the repair. Note: aiBestGuess": "Verify total R-134a charge from under-hood AC label / Aston Martin workshop manual (not available here)
14. 14

    Perform leak test and system verification
    With the system charged, start the engine and activate the AC at maximum cooling. Using UV dye (if previously added) or electronic leak detector, inspect all new connections for leaks. Check for proper compressor engagement, appropriate high and low side pressures on manifold gauges compared against the Aston Martin workshop manual values for the 2009 DB9 at the current ambient temperature, and cold air output from cabin vents (typically 40-50°F). Allow system to run for 10 minutes and recheck all connections for leaks or oil weeping. Note: appropriate high and low side pressures on manifold gauges per OEM specification for the ambient temperature (reference the DB9 service data pressure-temperature chart rather than generic values) Note: Check for proper compressor engagement, and verify high and low side pressures on manifold gauges fall within the OEM-specified ranges for the 2009 DB9 at the measured ambient temperature, along with cold air output from the cabin vents.

Reassembly

1. Reassembly is covered in the procedural steps above
2. Verify all hose mounting brackets are secure and the hose does not contact any moving or hot components
3. Confirm all protective panels and engine cover are properly installed
4. Double-check all AC line fittings are tightened to specification and show no signs of leakage

Verification

• Start engine and activate AC system at maximum cooling with recirculation mode on
• Verify compressor engages and disengages normally in response to temperature demands
• Confirm center dash vents produce air temperature between 40-50°F within 5 minutes of operation
• Check that no unusual noises or vibrations are present from the AC system
• Inspect all new hose connections visually for oil weeping or refrigerant leaks
• Verify AC system maintains proper cooling performance after 15-20 minutes of continuous operation
• If equipped with dual-zone climate control, verify both zones function correctly

More procedures for this vehicle