Replace the AC high pressure switch located on the liquid line near the condenser to restore proper AC system operation and safety monitoring.

Warnings

Tools required

Parts

• AC high pressure switch × 1 — Ford part SW-1858 or equivalent
• O-ring seal for pressure switch × 1 — Use OEM specification
• R-134a refrigerant × 1 — Per system capacity label
• PAG 46 oil × 1 — For EcoBoost AC system

Preparation

1. Ensure engine is completely cool to the touch
2. Park vehicle on level surface and apply parking brake
3. Disconnect negative battery cable to prevent accidental fan activation
4. Locate AC high pressure switch on liquid line between condenser and evaporator (driver side near radiator support)
5. Note system refrigerant capacity from underhood label (typically 1.75-2.0 lbs for this system)

Procedure

1. 1

   Recover AC refrigerant
   Connect AC recovery machine to service ports. Follow machine instructions to fully recover all refrigerant from the system. Verify system pressure reads 0 psi on manifold gauges before proceeding. Record amount of refrigerant recovered for recharge reference.
2. 2

   Access the high pressure switch
   Remove engine cover if equipped by pulling upward on front clips. The high pressure switch is located on the liquid line near the receiver-dryer on the driver side of the engine bay, forward of the engine. May need to move aside wiring harness clips for clear access.
3. 3

   Disconnect electrical connector
   Press the release tab on the electrical connector and pull straight away from the pressure switch. Use small flathead screwdriver to release locking tab if needed. Inspect connector terminals for corrosion or damage.
4. 4

   Remove pressure switch
   Using 19mm wrench, turn the pressure switch counterclockwise to remove from the liquid line fitting. Work may be tight due to EcoBoost turbocharger proximity. Remove and discard old O-ring seal from fitting port.
5. 5

   Prepare new switch installation
   Inspect liquid line port threads for damage or debris. Clean port opening with lint-free cloth. Install new O-ring seal onto new pressure switch. Lightly coat O-ring with fresh PAG 46 oil (2-3 drops) to prevent damage during installation.
6. 6

   Install new pressure switch
   Thread new pressure switch into liquid line port by hand until seated. Tighten to 20.0 Nm (15.0 lb-ft) using torque wrench. Do not overtighten as this can crack the switch housing or damage the port.
   ⚠Overtightening can crack the pressure switch housing or strip aluminum threads in the line fitting.
   Torque spec

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

   Reconnect electrical connector
   Push electrical connector firmly onto new pressure switch until locking tab clicks into place. Tug gently to verify secure connection. Ensure connector seal is properly seated to prevent moisture intrusion.
8. 8

   Evacuate AC system
   Connect vacuum pump to AC system service ports. Evacuate system to full vacuum (minimum 29 inches Hg) and hold for 30 minutes. System should maintain vacuum without rising, indicating no leaks. If vacuum drops, inspect switch installation for leaks.
9. 9

   Recharge AC system
   With system under vacuum, charge AC system with R-134a refrigerant to specification listed on underhood label (typically 1.75-2.0 lbs for 3.5L EcoBoost). Add PAG 46 oil if total amount recovered was significantly less than 8 oz. Use charging scale for accurate weight measurement.
10. 10

    Reconnect battery and test
    Reconnect negative battery cable. Start engine and turn AC to maximum cold, high blower speed. Monitor system pressures with manifold gauges. Low side should stabilize at 25-35 psi, high side at 200-250 psi at idle with ambient temp 70-80°F. Verify pressure switch operation by observing compressor clutch engagement.

Reassembly

1. Reinstall engine cover by aligning rear tabs first, then pressing down on front clips until seated
2. Verify all wiring harness clips are properly secured and routed away from hot engine components
3. Check for any tools or parts left in engine bay before closing hood

Verification

• Start engine and activate AC system. Verify cold air output from vents within 2-3 minutes
• Monitor AC system pressures with gauges: low side 25-35 psi, high side 200-250 psi at idle (ambient 70-80°F)
• Verify compressor clutch cycles normally and does not short-cycle
• Inspect pressure switch and surrounding fittings for refrigerant oil leaks after 10 minutes of operation
• Use electronic leak detector around new pressure switch to confirm no refrigerant leaks
• Test AC performance at highway speed to verify high pressure switch does not trip under load

More procedures for this vehicle