Replace the AC high pressure switch on a 2021-2024 Ford F-150 3.5L EcoBoost to restore proper AC system pressure monitoring and compressor control.

Warnings

Tools required

Parts

• AC high pressure switch × 1 — Use OEM specification
• AC high pressure line O-ring × 1 — Use OEM specification
• R-134a or R-1234yf refrigerant × 1 — Verify label under hood for refrigerant type

Fluids

• PAG 46 refrigerant oil — 0.25 qt

Preparation

1. Park vehicle on level surface and turn off engine
2. Verify refrigerant type from the label under the hood (R-134a or R-1234yf)
3. Ensure AC system has been off for at least 30 minutes to equalize pressure
4. Set up AC recovery machine appropriate for the refrigerant type in your vehicle

Procedure

1. 1

   Recover AC refrigerant
   Connect AC recovery machine to the low and high pressure service ports. Follow machine manufacturer instructions to completely recover all refrigerant from the system. Record the amount of refrigerant and oil recovered for refill reference.
2. 2

   Locate high pressure switch
   Open the hood and locate the AC high pressure switch on the high pressure line near the AC condenser on the driver side of the engine bay. The switch is a round sensor with an electrical connector on top, threaded into the high pressure line.
3. 3

   Disconnect electrical connector
   Press the tab on the electrical connector and pull it straight off the high pressure switch. Move the connector aside to prevent damage during switch removal.
4. 4

   Remove high pressure switch
   Using a 19mm wrench, turn the high pressure switch counterclockwise to unthread it from the high pressure line. Remove the switch completely. Have a shop towel ready to catch any residual oil that may drip from the port.
5. 5

   Remove and inspect old O-ring
   Remove the old O-ring from the switch port using an O-ring pick if necessary. Inspect the sealing surface in the high pressure line for any damage, debris, or contamination. Clean the sealing surface with a lint-free shop towel if needed.
6. 6

   Install new O-ring
   Install the new O-ring onto the new high pressure switch. Lightly coat the O-ring with fresh PAG refrigerant oil (PAG 46) to ensure proper sealing and prevent O-ring damage during installation.
7. 7

   Install new high pressure switch
   Thread the new high pressure switch into the high pressure line by hand until finger-tight. Using a 19mm wrench and torque wrench, tighten the switch to the specification for AC line fittings.
   Torque spec

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

   Reconnect electrical connector
   Push the electrical connector onto the new high pressure switch until it clicks into place. Ensure the connector is fully seated and the locking tab is engaged.
9. 9

   Evacuate AC system
   Connect the AC vacuum pump to the system service ports. Evacuate the system for a minimum of 30 minutes to remove all air and moisture. Monitor vacuum gauge to ensure system holds vacuum, indicating no leaks.
10. 10

    Recharge AC system
    Using the AC refrigerant scale and charging machine, recharge the system with the correct type and amount of refrigerant as specified on the under-hood label. Add PAG oil if total amount recovered was less than expected (typically add 1-2 oz to compensate for oil lost with old switch).

Reassembly

1. Verify all electrical connections are secure and properly seated
2. Ensure no tools or shop towels were left in the engine bay
3. Close hood securely

Verification

• Start the engine and turn on the AC system to maximum cold setting
• Verify the AC compressor engages and cycles normally
• Check for proper cold air output from cabin vents (typically 40-50°F at vents)
• Inspect the high pressure switch area for any signs of refrigerant leaks (oil residue)
• Use a leak detector around the switch connection to verify no refrigerant leaks
• Verify no warning lights or AC-related fault codes are present
• Test AC operation at idle and higher RPM to confirm proper system pressure and compressor cycling

More procedures for this vehicle