Replace the low-side AC hose on a 2015-2020 Ford F-150 with 3.5L EcoBoost engine, requiring evacuation and recharge of the AC system.

Warnings

Tools required

Parts

• AC low-side hose assembly × 1 — Use OEM Ford specification for 3.5L EcoBoost
• AC line O-rings × 4 — Use OEM specification, verify size compatibility
• R-134a refrigerant × 1 — Approximately 1.75 lbs total system capacity
• PAG 46 compressor oil × 1 — Use Ford-approved PAG oil

Preparation

1. Park vehicle on level surface and engage parking brake
2. Allow engine to cool completely if recently operated
3. Disconnect negative battery terminal to prevent electrical issues
4. Recover all refrigerant from AC system using certified AC machine and document amount recovered
5. Verify system pressure reads 0 PSI before proceeding with line disconnection
6. Locate low-side AC hose routing from accumulator/drier to compressor on passenger side of engine bay

Procedure

1. 1

   Remove engine cover and access components
   Remove the plastic engine cover by pulling upward on the cover to release the retaining grommets. Set aside. This provides better access to the AC lines on the passenger side of the engine.
2. 2

   Disconnect low-side line at accumulator/drier
   Locate the low-side line connection at the accumulator/drier assembly near the firewall on the passenger side. Use the appropriate spring lock coupling tool to compress the spring lock mechanism. While holding the tool in place, pull the line away from the accumulator. Cap both openings immediately to prevent contamination. Remove and discard the old O-rings from the connection.
3. 3

   Disconnect low-side line at compressor
   Locate the low-side line connection on the AC compressor mounted low on the passenger side of the engine. Clean the area around the fitting with a shop towel. Use the appropriate wrench to loosen and disconnect the line fitting from the compressor. Allow any residual oil to drain into a pan and measure the amount. Cap the compressor port immediately. Remove and discard the old O-rings.
   Torque spec

   AC Line Fittings20 Nm (15 lb-ft)
4. 4

   Remove line mounting brackets
   Trace the low-side hose routing and locate all mounting brackets and clips securing the hose to the engine and frame. Remove bolts or release clips as needed. On the 3.5L EcoBoost, there are typically 2-3 mounting points along the hose run. Keep hardware organized for reinstallation.
   Torque spec

   Mounting Bolts31 Nm (23 lb-ft)
5. 5

   Remove old low-side hose
   Carefully maneuver the old low-side hose out of the engine bay, noting the exact routing path, bracket locations, and orientation of connections. Take photos if needed for reference during installation. Inspect the old hose for signs of damage, abrasion, or leak points to identify root cause of failure.
6. 6

   Prepare new low-side hose
   Remove protective caps from the new low-side hose assembly. Install new O-rings on both connection points of the hose. Lubricate all new O-rings with clean PAG 46 oil. Add the appropriate amount of fresh PAG oil to the new hose (typically 1-2 oz) to replace what was lost with the old hose, matching the amount that drained out earlier.
7. 7

   Route new low-side hose
   Route the new low-side hose through the engine bay following the exact same path as the original hose. Ensure the hose does not contact any sharp edges, hot components, or moving parts. Verify adequate clearance from the serpentine belt, exhaust manifolds, and engine mounts.
8. 8

   Connect hose to compressor
   Remove the cap from the compressor low-side port. Verify the new lubricated O-ring is properly seated on the hose fitting. Align and hand-thread the fitting into the compressor port, ensuring proper engagement before tightening. Use a torque wrench to tighten the fitting to specification.
   Torque spec

   AC Line Fittings20 Nm (15 lb-ft)
9. 9

   Connect hose to accumulator/drier
   Remove the cap from the accumulator/drier connection. Verify the new lubricated O-rings are properly seated in the spring lock coupling. Push the hose fitting firmly into the accumulator port until you hear and feel the spring lock mechanism engage. Gently pull back on the hose to verify it is locked in place and cannot be removed without the disconnect tool.
10. 10

    Secure mounting brackets
    Install all mounting brackets and clips in their original locations. Ensure the hose is properly supported and does not have excessive slack or tension. Torque mounting bolts to specification. Double-check that the hose routing maintains adequate clearance from all moving and hot components.
    Torque spec

    Mounting Bolts31 Nm (23 lb-ft)
11. 11

    Perform system leak test
    Connect the AC service machine to the vehicle. Evacuate the system to create a vacuum, holding for at least 30 minutes. Monitor vacuum gauge for any pressure rise that would indicate a leak. If the system holds vacuum without decay, proceed to recharge. If vacuum decays, locate and repair the leak before charging.
12. 12

    Recharge AC system
    Using the AC service machine, charge the system with the correct amount of R-134a refrigerant (refer to underhood decal for exact capacity, typically 1.75 lbs for 3.5L EcoBoost). Add refrigerant slowly through the low-side service port. Monitor system pressures during charging to ensure proper fill.

Reassembly

1. Reinstall engine cover by aligning grommets and pressing down firmly until seated
2. Reconnect negative battery terminal and tighten securely
3. Clear any diagnostic codes related to AC system using scan tool if needed

Verification

• Start engine and allow to idle for 2 minutes
• Turn AC system to MAX cooling with blower on high speed
• Verify cold air is produced from all vents within 3-5 minutes
• Check low-side pressure reads 25-45 PSI and high-side reads 175-250 PSI at idle with ambient temperature around 75-80°F
• Inspect all connection points for signs of refrigerant leaks using electronic leak detector or UV dye
• Listen for unusual noises from compressor or hissing sounds indicating leaks
• Verify compressor clutch engages and cycles normally during operation
• Test AC performance at idle and 2000 RPM to confirm adequate cooling at both speeds

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