AC Hose Assembly

This procedure covers the removal and replacement of the AC hose assembly on a 2007 Ram 3500 with the 5.9L Cummins diesel engine, including refrigerant recovery and system recharging.

Warnings

Tools required

Parts

• AC hose assembly × 1 — Use OEM specification for specific routing
• AC line O-rings × 4 — Use OEM specification
• PAG oil × 1 — PAG-46 for R-134a systems
• Plastic tie straps × 1 — Assorted sizes for routing

Fluids

• R-134a refrigerant

Preparation

1. Park vehicle on level ground and engage parking brake
2. Allow engine to cool completely if recently operated
3. Disconnect negative battery cable to prevent fan cycling during work
4. Identify which AC hose assembly requires replacement (suction, discharge, or liquid line)
5. Verify replacement hose matches original routing and fittings
6. Prepare AC recovery machine according to manufacturer instructions

Procedure

1. 1

   Recover AC refrigerant
   Connect AC recovery machine to the service ports on the high and low pressure sides. Follow recovery machine instructions to fully evacuate all refrigerant from the system. Verify recovery is complete by observing both gauges reading zero or vacuum. Document the amount of refrigerant recovered for proper recharge quantity.
2. 2

   Remove engine cover if equipped
   If vehicle has a plastic engine cover, remove fasteners and lift cover away to access engine bay components. Set aside in a clean location.
3. 3

   Locate and access AC hose assembly
   Trace the AC hose assembly from the compressor to the condenser and evaporator. On the 5.9L Cummins, the AC compressor is mounted on the engine accessory drive; verify its exact location (typically driver's side) before proceeding with access. Remove any plastic shields, air intake components, or battery tray that interfere with access to the hose connections. Cut any tie straps securing the hose to the chassis or other components.
4. 4

   Disconnect AC hose at compressor
   Using appropriate wrench sizes, loosen and remove the bolts securing the AC hose fitting to the compressor. The connection typically uses a flanged fitting with two bolts. Support the hose to prevent stress on other connections. Cap or plug the compressor port immediately to prevent moisture and contamination entry. Remove and discard the O-rings from the fitting.
5. 5

   Disconnect AC hose at condenser or evaporator end
   Locate the opposite end of the hose assembly at the condenser (front of vehicle near radiator) or evaporator connections (firewall area). Remove the bolts securing the fitting using appropriate wrenches. Support the hose during removal. Immediately cap or plug the open connection. Remove and discard the O-rings.
6. 6

   Remove AC hose assembly from vehicle
   Carefully route the old AC hose assembly out of the engine bay, noting the exact path and any mounting clips or brackets it passes through. Take photos if needed to document routing. Remove any remaining mounting brackets or clips attached to the hose.
7. 7

   Prepare new AC hose assembly
   Unpack new AC hose assembly and verify it matches the original configuration. Lubricate new O-rings with clean PAG-46 oil and install them in the proper grooves on both connection fittings. Add the manufacturer-recommended amount of PAG oil into the new hose (typically 1-2 oz depending on hose length) to replace oil lost with the old hose.
8. 8

   Install new AC hose assembly
   Route the new AC hose through the engine bay following the exact path of the original hose. Ensure the hose does not contact hot exhaust components, sharp edges, or moving parts like the serpentine belt or cooling fan. Position all bends and curves to match original routing to prevent kinks or restrictions.
9. 9

   Connect AC hose at compressor
   Remove the cap from the compressor port and align the new AC hose fitting with the compressor connection. Ensure the O-rings are properly seated. Install and hand-tighten the connection bolts, then tighten to proper specification using a torque wrench. Since no torque specification is provided in the database, consult the factory service manual for the correct AC fitting torque for this vehicle before final tightening. Do not rely on generic values.
10. 10

    Connect AC hose at opposite end
    Remove the cap from the condenser or evaporator connection and align the AC hose fitting. Verify O-rings are properly positioned. Install connection bolts and tighten to the factory-specified torque for this vehicle's AC fittings; consult the service manual rather than using generic values.
11. 11

    Secure hose routing
    Install new plastic tie straps to secure the AC hose to original mounting points along the chassis, frame rails, or engine bay brackets. Ensure the hose has no contact with moving components and maintains clearance from the exhaust system. Check that hose routing allows for engine movement without stress on connections.
12. 12

    Evacuate AC system
    Connect vacuum pump to AC system service ports using manifold gauges. Evacuate the system to pull a deep vacuum (minimum 29 inches Hg). Maintain vacuum for at least 30 minutes to remove all moisture. Close valves and observe gauges for 10 minutes to verify system holds vacuum without rising pressure, which would indicate a leak.
13. 13

    Recharge AC system
    With vacuum verified, recharge the AC system with R-134a refrigerant to the factory-specified capacity. For the 2007 Ram 3500 with 5.9L Cummins, verify the exact refrigerant charge quantity on the underhood A/C label or in the factory service manual, as capacity varies with front-only vs. front/rear air configurations. Charge through the low-side port only with engine running and AC on maximum cold setting. Monitor pressures to ensure proper charging.
14. 14

    Leak test system
    With system charged, use an electronic refrigerant leak detector to check all connections for leaks, including both ends of the new hose assembly. Pay particular attention to the O-ring seal areas. If leaks are detected, recover refrigerant, correct the issue, and repeat evacuation and charging procedures.

Reassembly

1. Reinstall any air intake components, shields, or battery tray removed during access
2. Reinstall engine cover if equipped, ensuring all fasteners are secure
3. Reconnect negative battery cable
4. Start engine and verify AC compressor engages properly

Verification

• Start engine and turn AC system to maximum cold with blower on high
• Verify AC compressor clutch engages and remains engaged
• Check that both AC lines at the compressor show appropriate temperature difference (suction line cold, discharge line hot)
• Measure vent temperature after 5 minutes of operation; should be 35-45°F depending on ambient conditions
• Verify no unusual noises from compressor or AC system
• Re-check all connections for refrigerant leaks using leak detector after system reaches operating temperature
• Verify AC system maintains proper cooling performance during test drive

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