AC Hose - High Side

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

Warnings

Tools required

Parts

• AC high-side hose assembly × 1 — Use OEM specification
• AC line O-rings × 4 — Check hose kit or order separately
• PAG oil for AC system × 1 — Match compressor type

Fluids

• R-134a

Preparation

1. Park vehicle on level surface and set parking brake
2. Allow engine to cool completely if recently operated
3. Gather all tools and replacement parts before beginning
4. Verify replacement hose matches original routing and fittings
5. Ensure AC recovery machine is properly certified and operational

Procedure

1. 1

   Recover AC refrigerant
   Connect AC recovery machine to service ports on the AC system. Follow recovery machine instructions to completely evacuate all R-134a refrigerant from the system. Record the amount of refrigerant recovered for recharge reference. Ensure recovery is complete before proceeding.
2. 2

   Locate high-side AC hose
   Open hood and identify the high-side AC hose. It runs from the AC compressor discharge port (on passenger side of engine) to the condenser at the front of the vehicle. The high-side discharge line carries high-pressure refrigerant and will be warm/hot during AC operation; confirm identification by tracing it from the compressor discharge port to the condenser inlet rather than relying on diameter alone. Trace the entire hose routing to identify all connection points and mounting clips.
3. 3

   Disconnect hose at compressor
   Using appropriate line wrenches, disconnect the high-side hose from the AC compressor discharge fitting. Hold the compressor fitting stationary with one wrench while loosening the hose nut with the other to prevent damage to compressor threads. Have a shop towel ready to catch any residual oil. Remove and discard the O-ring seals.
4. 4

   Disconnect hose at condenser
   Access the condenser connection at the front of the vehicle. You may need to reach down from above or access from underneath. Use line wrenches to disconnect the high-side hose from the condenser inlet. Hold the condenser fitting stationary while loosening the hose nut. Catch any residual oil with shop towels. Remove and discard the O-ring seals.
5. 5

   Remove hose mounting hardware
   Release any mounting clips, brackets, or retainers securing the high-side hose to the engine bay or frame. Note the exact routing and position of all clips for reinstallation. On the Cummins engine, the hose may be clipped to the intake plumbing or firewall area.
6. 6

   Remove old hose
   Carefully remove the high-side hose from the vehicle, noting its exact routing path. Take photos if necessary to ensure proper routing of the replacement hose. Inspect the old hose for signs of damage, abrasion, or the source of any leaks.
7. 7

   Inspect fittings and components
   Inspect the compressor discharge fitting and condenser inlet fitting for damage, corrosion, or debris. Clean the fitting surfaces with a clean shop towel. Check that O-ring sealing surfaces are smooth and undamaged. Replace any damaged fittings before proceeding.
8. 8

   Prepare new hose
   Unpack the new high-side hose and verify it matches the original in length, routing, and fitting types. Install new O-rings on both ends of the hose, lightly lubricating them with clean PAG oil suitable for R-134a systems. Do not use petroleum-based lubricants.
9. 9

   Route and install new hose
   Route the new high-side hose following the exact path of the original. Ensure the hose does not contact hot engine components, sharp edges, or moving parts. Reinstall all mounting clips and brackets to secure the hose properly and prevent vibration or chafing.
10. 10

    Connect hose to compressor
    Thread the hose fitting onto the compressor discharge port by hand first to ensure proper alignment. Once hand-tight, use line wrenches to tighten the connection. Hold the compressor fitting stationary while tightening the hose nut. Tighten snugly but do not over-torque, as this can damage the O-rings or fittings.
11. 11

    Connect hose to condenser
    Thread the hose fitting onto the condenser inlet port by hand first. Once hand-tight, use line wrenches to tighten the connection while holding the condenser fitting stationary. Tighten to the manufacturer-specified torque (verify exact spec in the factory service manual for this fitting size) to ensure a leak-free seal.
12. 12

    Evacuate AC system
    Connect AC vacuum pump to service ports. Evacuate the system to at least 29 inches of mercury (vacuum) and hold for minimum 30 minutes to remove all air and moisture. If vacuum does not hold, there is a leak that must be repaired before proceeding.
13. 13

    Recharge AC system
    Using AC manifold gauges and refrigerant scale, recharge the system to the factory-specified R-134a charge weight for this vehicle (verify exact charge amount on the underhood AC label or factory service manual); use the recorded recovered amount only as a cross-reference. Add appropriate amount of PAG oil if specified by hose replacement guidelines. Do not overcharge the system.

Reassembly

1. Verify all AC line connections are properly tightened and secured
2. Ensure all mounting clips and brackets are reinstalled to prevent hose movement
3. Double-check hose routing to confirm no contact with hot or moving components

Verification

• Start engine and turn AC to maximum cold with high blower speed
• Verify AC compressor engages and system produces cold air within 2-3 minutes
• Check high-side and low-side pressures with manifold gauges to confirm proper system operation
• Use refrigerant leak detector or soap solution to check all connections for leaks, especially at the new hose fittings
• Verify system maintains proper cooling performance during a 10-15 minute test drive
• Inspect hose routing one final time with engine running to ensure no contact with moving components

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