AC Orifice Tube

This procedure replaces the AC orifice tube, a filter/metering device in the AC system that regulates refrigerant flow and filters debris. Requires AC system evacuation and recharge.

Warnings

Tools required

Parts

• AC orifice tube × 1 — Use OEM specification
• AC line O-rings × 4 — Use OEM specification
• R-134a refrigerant × 1 — Typically 16-18 oz total system capacity
• PAG oil (ND-11) × 1 — Honda ND-11 PAG oil

Preparation

1. Ensure engine is completely cool before beginning work
2. Park vehicle on level surface and engage parking brake
3. Verify AC system refrigerant type is R-134a (2016-2021 Civic uses R-134a, not R-1234yf)
4. Connect AC recovery machine and fully evacuate refrigerant from system according to EPA guidelines
5. Measure and record amount of oil recovered to determine replacement quantity
6. Allow system pressure to equalize to atmospheric before disconnecting lines

Procedure

1. 1

   Locate and access orifice tube
   Open hood and locate the liquid line connection near the firewall on passenger side. The orifice tube is inside the liquid line at the inlet to the evaporator. Identify the connection point which has a larger diameter section where the tube housing sits. Clean area around the connection to prevent contamination.
2. 2

   Disconnect liquid line fitting
   Using a flare nut wrench to prevent rounding, carefully loosen and disconnect the liquid line fitting at the evaporator inlet. Some refrigerant oil will drain out - catch with shop towels and note approximate quantity. Inspect the connection for debris or metal particles which indicate AC system contamination.
   ⚠If metal debris is present in the oil, the entire AC system requires flushing and the compressor may be failing.
3. 3

   Remove old orifice tube
   Insert the orifice tube removal tool into the line opening. The tool should grip the tube's edges. Gently twist and pull to extract the orifice tube assembly. If the tube is stuck or breaks apart, use a specialized extraction tool or carefully use a pick to remove fragments. Ensure all pieces are removed including the filter screen.
   ⚠The orifice tube can break during removal if stuck. Take care not to push fragments deeper into the line.
4. 4

   Inspect old orifice tube
   Examine the removed orifice tube and filter screen for metal particles, excessive debris, or discoloration. Check if the brass filter screen is intact or damaged. Black debris indicates compressor clutch wear; metallic particles indicate compressor failure. If significant contamination exists, system flushing is required before proceeding.
5. 5

   Remove and replace O-rings
   Remove the old O-rings from both the liquid line fitting and the evaporator inlet connection. Use a pick if necessary but avoid scratching the sealing surfaces. Clean the sealing surfaces thoroughly with a lint-free cloth. Inspect for any scratches or damage to the metal sealing surfaces.
6. 6

   Prepare new orifice tube
   Remove new orifice tube from packaging immediately before installation. Verify the tube has the correct color coding for the 1.5L turbo engine (typically green or specific Honda designation). Check that the filter screen is intact and properly oriented with the tapered end pointing toward refrigerant flow direction (toward evaporator).
7. 7

   Lubricate and install new O-rings
   Coat new O-rings with fresh ND-11 PAG oil. Install new O-rings onto the liquid line fitting and evaporator connection, ensuring they seat properly in their grooves. Apply a thin coating of PAG oil to the O-ring surfaces to aid installation and initial sealing.
   ℹ️Use only ND-11 PAG oil specified for Honda AC systems. Do not mix oil types.
8. 8

   Install new orifice tube
   Apply a small amount of PAG oil to the outer O-rings on the new orifice tube. Insert the tube into the liquid line with the tapered end pointing toward the evaporator. Push firmly until the tube seats completely against the internal stop. The dimples on the tube body should be visible at the line opening, confirming proper seating depth.
9. 9

   Reconnect liquid line
   Align and hand-thread the liquid line fitting to the evaporator inlet connection. Ensure proper thread engagement before tightening. Using a torque wrench and flare nut wrench as backup, tighten the fitting to specification.
   Torque spec

   AC Line Fittings20 Nm (15 lb-ft)
10. 10

    Add replacement PAG oil
    Calculate oil replacement quantity: add the amount recovered during evacuation plus 1 oz for the new orifice tube. If less than 3 oz was recovered total, add 3 oz. Use AC oil injector to add ND-11 PAG oil through the low-side service port. If using manifold gauges, add through suction line.
11. 11

    Evacuate AC system
    Connect AC machine to service ports. Run vacuum pump for minimum 30 minutes to achieve deep vacuum (29+ inches Hg). Monitor for vacuum decay - system should hold vacuum for 10 minutes without drop, confirming no leaks. If vacuum drops, locate and repair leak before recharging.
12. 12

    Recharge AC system
    With system under vacuum, charge with R-134a refrigerant per specifications (typically 16-18 oz for 1.5L turbo - verify on underhood label). Charge liquid refrigerant into high side with engine off, then start engine and add remaining through low side if needed. Monitor pressures to ensure proper charge level.

Reassembly

1. Verify all AC line connections are properly torqued and secure
2. Confirm no tools or shop towels are left in engine bay
3. Double-check that service port caps are reinstalled on both high and low side ports

Verification

• Start engine and set AC to maximum cold, maximum fan speed
• Verify compressor clutch engages and remains engaged
• Check that center vent temperature reaches 40-45°F within 5 minutes at idle
• Inspect all connections for signs of oil leakage indicating refrigerant leak
• Verify low side pressure is 25-35 PSI and high side is 200-250 PSI at idle with ambient temperature 75-85°F
• Listen for unusual noises from compressor indicating contamination or insufficient oil
• Use electronic leak detector around all disturbed connections to confirm no leaks
• Test AC performance during short test drive to ensure consistent cooling

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