AC Hose - Low Side

This procedure covers the replacement of the low-side AC hose on the 2016-2021 Honda Civic 1.5L Turbo, including refrigerant recovery, hose removal, installation with new O-rings, and system recharge.

Warnings

Tools required

Parts

• AC low-side hose assembly × 1 — Use OEM Honda part number for 1.5L Turbo model
• AC line O-rings (various sizes) × 1 — Honda AC O-ring kit
• R-134a refrigerant × 1 — Verify capacity on underhood label
• PAG 46 oil × 1 — Honda-approved PAG oil

Preparation

1. Park vehicle on level surface and apply parking brake
2. Ensure engine is completely cool before beginning work
3. Verify you have EPA-certified AC recovery equipment and certification to perform refrigerant service
4. Locate the AC system refrigerant capacity label on the underside of the hood
5. Photograph routing of AC hoses before disassembly for reference during installation
6. Prepare new O-rings and PAG oil for installation

Procedure

1. 1

   Recover AC refrigerant
   Connect AC recovery machine to the service ports. Follow recovery machine instructions to completely evacuate all R-134a refrigerant from the system. Record the amount of refrigerant and oil recovered. Ensure recovery machine indicates complete evacuation before proceeding.
   ⚠️Never disconnect AC lines with refrigerant still in the system. Pressurized refrigerant can cause severe injury.
2. 2

   Access low-side AC hose
   Open hood and locate the low-side AC hose running from the firewall to the compressor on the passenger side of the engine bay. Remove the plastic engine cover by pulling upward on the retaining clips. If necessary, remove air intake components for better access to the hose routing.
3. 3

   Disconnect low-side hose at compressor
   Using a 12mm flare nut wrench, carefully loosen the low-side hose connection at the AC compressor. Support the compressor-side fitting with a backup wrench to prevent turning the compressor port. Once loose, unthread by hand and separate the connection. Immediately cap or plug both openings to prevent contamination.
   ⚠Use a flare nut wrench to prevent rounding of the AC line fitting. Standard wrenches may damage the soft aluminum fittings.
4. 4

   Disconnect low-side hose at evaporator/firewall
   Locate the firewall connection point for the low-side hose near the passenger side. Use a 12mm flare nut wrench to loosen the fitting at the evaporator line. Again, use a backup wrench on the stationary side to prevent line twisting. Remove the connection and cap both openings.
5. 5

   Remove hose mounting brackets
   Remove any mounting clips or brackets securing the low-side hose to the chassis or engine components. These are typically 10mm bolts or push-pin clips. Note the exact routing and clip positions for proper reinstallation of the new hose.
   Torque spec

   Mounting Bolts26 Nm (19 lb-ft)
6. 6

   Extract old hose assembly
   Carefully pull the old low-side hose from the engine bay, following the routing path. Take care not to damage surrounding components or wiring harnesses. Inspect the old hose for signs of wear, damage, or oil residue that may indicate the leak location.
7. 7

   Inspect and clean connection points
   Remove the caps from the compressor and evaporator line ports. Inspect all connection surfaces for debris, corrosion, or damage. Clean the mating surfaces with a lint-free cloth. Check that the O-ring sealing surfaces are smooth and free of scratches or scoring.
   ⚠Any debris entering the AC system can damage the compressor and other components. Keep all openings capped when not working on them.
8. 8

   Install new O-rings with PAG oil
   Remove all old O-rings from the connection fittings on both the compressor and evaporator sides. Install new O-rings from the kit onto the new AC hose fittings. Coat each O-ring with a thin film of fresh PAG 46 oil using a clean finger. Also add 1-2 drops of PAG oil into each port before connection.
   ℹ️Never reuse old AC O-rings. Always use new O-rings coated with PAG oil to ensure proper seal and prevent leaks.
9. 9

   Route new low-side hose
   Following the routing documented during removal, carefully route the new low-side AC hose through the engine bay. Ensure the hose follows the same path and does not contact any sharp edges, hot exhaust components, or moving parts. Verify adequate clearance from the serpentine belt and pulleys.
10. 10

    Connect hose at evaporator/firewall
    Thread the new hose fitting onto the evaporator line connection at the firewall by hand until finger-tight. Use a 12mm flare nut wrench with a backup wrench to tighten the AC line fitting to the specified torque. Do not overtighten, as this can damage the O-ring seal.
    ⚠AC line fittings are aluminum and easily damaged. Tighten to exact torque specification using a torque wrench.
    Torque spec

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

    Connect hose at compressor
    Thread the low-side hose fitting onto the AC compressor port by hand until finger-tight. Using a torque wrench and 12mm socket or flare nut wrench, tighten the AC line fitting to specification while holding the compressor port with a backup wrench.
    Torque spec

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

    Reinstall mounting brackets
    Secure the new AC hose to all original mounting points using the brackets and clips removed earlier. Ensure the hose is properly supported and cannot vibrate against other components. Tighten mounting bolts to specification.
    Torque spec

    Mounting Bolts26 Nm (19 lb-ft)
13. 13

    Vacuum test the AC system
    Connect the AC vacuum pump to the system via the service ports. Evacuate the system to at least 29 inches of mercury (inHg) vacuum and hold for minimum 30 minutes. Monitor the vacuum gauge; if vacuum holds steady, the system has no leaks. If vacuum drops, locate and repair the leak before proceeding.
    ⚠Proper vacuum is essential to remove all moisture from the AC system. Moisture can freeze and damage components or react with refrigerant to form corrosive acids.
14. 14

    Recharge AC system
    Using an electronic refrigerant scale and the manifold gauge set, recharge the AC system with the exact amount of R-134a specified on the underhood label (typically 15-17 oz for this model). Add the appropriate amount of PAG oil to replace what was lost with the old hose (typically 1-2 oz if minimal oil was recovered). Follow proper charging procedures for accurate fill.
15. 15

    Test AC operation and check for leaks
    Start the engine and turn the AC system to maximum cooling. Allow the system to run for 5-10 minutes. Monitor gauge pressures to ensure they are within normal range (low side: 25-40 PSI, high side: 150-250 PSI depending on ambient temperature). Use an electronic leak detector or UV light to check all new connections for leaks. Verify cold air output at cabin vents.
    ℹ️Normal AC pressures vary with ambient temperature and humidity. Consult factory service data for expected pressure ranges at current conditions.

Reassembly

1. Reinstall any air intake components that were removed for access
2. Reinstall the plastic engine cover, ensuring all clips are properly seated
3. Verify all tools and materials are removed from the engine bay
4. Close the hood and perform a final visual inspection of the engine compartment

Verification

• Start the engine and run the AC on maximum cooling for at least 10 minutes
• Verify cold air output at all cabin vents (should be 40-50°F colder than ambient)
• Check that AC compressor engages and disengages properly with AC button
• Inspect all AC line connections for any signs of oil residue or refrigerant leaks
• Verify AC system pressures are within manufacturer specifications using gauge set
• Listen for any unusual noises from the compressor or AC system during operation
• Confirm no error codes are present in the climate control system
• Test-drive the vehicle to ensure AC performs properly under load and various conditions

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