AC Orifice Tube

This procedure replaces the AC orifice tube, a filter/metering device located in the liquid line between the condenser and evaporator, to restore proper AC cooling performance.

Warnings

Tools required

Parts

• AC orifice tube with screen × 1 — Use OEM specification
• AC line O-rings × 4 — Use OEM specification
• PAG 46 refrigerant oil × 1 — Use OEM specification
• R-134a refrigerant × 1 — Typically 1.5-2.0 lbs

Preparation

1. Park vehicle on level ground and engage parking brake
2. Turn engine off and allow AC system to equalize pressure for at least 30 minutes
3. Have AC system professionally recovered using certified recovery equipment or use your own recovery machine to capture all refrigerant
4. Note the amount of refrigerant and oil recovered for proper recharge quantities
5. Verify system pressure is at 0 PSI before proceeding with line disconnection

Procedure

1. 1

   Access the liquid line assembly
   Locate the liquid line running from the condenser (front of vehicle) to the evaporator (firewall). On the 2015-2020 F-150, the orifice tube is typically located in the liquid line near the firewall on the passenger side, upstream of the evaporator inlet. You may need to remove the engine cover or move aside wiring harnesses for better access.
2. 2

   Disconnect the liquid line at the orifice tube location
   Identify the spring-lock coupling or threaded fitting closest to the orifice tube location. If equipped with spring-lock couplings, use the appropriate disconnect tool to release the coupling. If threaded, use a line wrench to loosen the fitting. Cap open lines immediately with plugs to prevent moisture and debris entry. Some residual refrigerant oil will drain out - capture with shop towels.
   ⚠Even after recovery, small amounts of refrigerant may remain. Work slowly and allow any residual pressure to vent safely.
3. 3

   Remove old orifice tube
   Insert the orifice tube removal tool into the line where the tube is located (typically in the line leading to the evaporator). The orifice tube has a conical screen that may be stuck in the line due to debris or corrosion. Carefully thread the removal tool onto the orifice tube body and pull straight out with steady pressure. If the tube breaks, use a pick tool to remove all fragments including the brass mesh screen. Inspect the removed tube for debris, metal particles, or discoloration which indicates compressor failure.
   ⚠If metal shavings or debris are found in the orifice tube screen, the compressor may be failing. Inspect the entire system and consider flushing before installing new tube.
4. 4

   Clean the line bore
   Using a clean lint-free shop towel and possibly a small amount of refrigerant oil, carefully clean the inside of the liquid line bore where the orifice tube seats. Remove any debris, old O-ring material, or contamination. Do not allow any debris to fall into the line. Inspect for damage or scoring that could prevent proper seating.
5. 5

   Install new orifice tube
   Lightly coat the new orifice tube O-rings with fresh PAG 46 refrigerant oil. Note the directional arrow on the orifice tube body - it must point in the direction of refrigerant flow (toward the evaporator). Insert the tube into the line by hand, ensuring it seats fully against the internal stop. The tube should insert smoothly without excessive force. Verify the tube is fully seated and cannot be pulled back out easily.
6. 6

   Replace line O-rings
   Remove the old O-rings from both sides of the disconnected line fittings. Inspect the sealing surfaces for damage or scoring. Install new O-rings into the proper grooves and coat lightly with PAG 46 refrigerant oil. Ensure O-rings are properly seated in their grooves and not twisted.
   Torque spec

   AC Line Fittings20 Nm (15 lb-ft)
7. 7

   Reconnect liquid line
   Reconnect the liquid line at the disconnection point. For spring-lock couplings, push together firmly until you hear/feel the lock engage, then pull to verify connection. For threaded fittings, hand-tighten first, then torque to specification using a line wrench to prevent rounding. Ensure lines are properly routed without kinks or excessive tension.
   Torque spec

   AC Line Fittings20 Nm (15 lb-ft)
8. 8

   Evacuate the AC system
   Connect the AC recovery/evacuation/recharge machine to the service ports. Evacuate the system for a minimum of 30 minutes to remove all air and moisture. A proper evacuation should pull the system down to 29+ inches of mercury (Hg) vacuum. After evacuation, close the valves and watch the gauge for 10 minutes - vacuum should hold steady indicating no leaks.
   ℹ️Proper evacuation is critical to remove moisture which can cause AC system corrosion and reduced performance.
9. 9

   Recharge the AC system
   Recharge the system with the amount of R-134a refrigerant noted during recovery (typically 1.5-2.0 lbs for the F-150 5.0L, verify on underhood label). Add the appropriate amount of PAG 46 oil to compensate for oil lost during component replacement (typically 1-2 oz for orifice tube replacement). Follow the recharge machine instructions or use the low-side port for vapor charging and high-side for liquid charging with engine off.
   ⚠Do not overcharge the system. Verify correct refrigerant capacity on the underhood AC specification label.
10. 10

    Perform leak check
    With the system charged, start the engine and turn AC to maximum cold with fan on high. Using an electronic leak detector or soapy water solution, check all connections including the liquid line fittings you disconnected. Look for bubbles or detector alerts. Pay special attention to the area where the orifice tube is installed. Allow system to run for 5-10 minutes and recheck.

Reassembly

1. Reinstall any engine covers or components removed for access
2. Secure any wiring harnesses or hoses that were moved aside
3. Verify all AC line connections are tight and properly routed without interference

Verification

• With engine running and AC on maximum cold, verify both high and low side pressures are within specification (typically 150-250 PSI high side, 25-45 PSI low side at idle depending on ambient temperature)
• Verify cold air is blowing from vents - center vent temperature should be 35-45°F with 70-80°F ambient temperature
• Listen for unusual noises from the compressor indicating debris or restriction
• Verify no refrigerant odor is present indicating leaks
• Recheck all connections after 24 hours of operation for any delayed leaks

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