AC High Pressure Switch

This procedure covers the removal and replacement of the AC high pressure switch on a 2016-2021 Honda Civic with the 1.5L turbo engine, requiring refrigerant recovery and system recharge.

Warnings

Tools required

Parts

• AC high pressure switch × 1 — Use OEM Honda part or equivalent
• AC line O-rings × 2 — Use OEM specification
• PAG oil for AC system × 1 — ND-11 or equivalent

Preparation

1. Ensure engine is completely cool before beginning work
2. Park vehicle on level surface and engage parking brake
3. Disconnect negative battery terminal to prevent accidental fan operation
4. Connect AC recovery machine to service ports and fully recover refrigerant according to machine instructions
5. Record the amount of refrigerant recovered for proper recharge quantity

Procedure

1. 1

   Locate AC high pressure switch
   Open hood and locate the AC high pressure switch on the high-pressure AC line near the condenser on the passenger side of the engine bay. The switch is a small cylindrical sensor with a single electrical connector threaded into the AC line.
2. 2

   Disconnect electrical connector
   Press the locking tab on the electrical connector and pull straight off the AC high pressure switch. Move the wiring harness aside to prevent contamination during line disconnection.
3. 3

   Remove high pressure switch
   Using a 12mm wrench or appropriate socket, carefully unthread the AC high pressure switch from the AC line. Be prepared for a small amount of residual refrigerant oil to leak. Immediately cap or plug the line opening to prevent moisture contamination.
4. 4

   Inspect and clean threads
   Inspect the threaded port in the AC line for damage or debris. Clean threads with a lint-free cloth. Check the condition of the O-ring sealing surface and ensure no contamination is present.
5. 5

   Prepare new switch
   Remove new AC high pressure switch from packaging. Install new O-rings onto the switch threads if not pre-installed. Apply a small amount of fresh PAG oil (approximately 2-3 drops) to the O-rings to aid installation and prevent damage.
6. 6

   Install new high pressure switch
   Thread the new AC high pressure switch into the AC line by hand until seated, ensuring proper alignment to avoid cross-threading. Tighten to specification using a torque wrench.
   Torque spec

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

   Reconnect electrical connector
   Push the electrical connector onto the new AC high pressure switch until the locking tab clicks into place. Gently tug to verify secure connection.
8. 8

   Evacuate AC system
   Connect AC service machine to both high and low pressure ports. Evacuate the system for a minimum of 30 minutes to remove all moisture and air. Monitor vacuum gauge to ensure system holds vacuum, indicating no leaks.
9. 9

   Recharge AC system
   Recharge the AC system with the recorded amount of R-134a refrigerant (typically 16-18 oz total capacity). Add PAG oil if significant oil was lost during service (typically 1-2 oz if only switch was replaced).
10. 10

    Reconnect battery and test
    Reconnect negative battery terminal. Start engine and activate AC system to maximum cooling. Monitor system pressures and verify high pressure switch operation using a scan tool or by observing proper compressor cycling.

Reassembly

1. Ensure all electrical connectors are fully seated and locked
2. Verify no tools or shop towels remain in engine bay
3. Check for any refrigerant leaks around the new switch using a leak detector or soap solution

Verification

• Confirm AC system cools effectively with proper vent temperatures (typically 38-45°F at center vents on recirculation mode)
• Monitor AC pressures: low side should be 25-35 PSI, high side 200-250 PSI at idle with AC on maximum (ambient temperature dependent)
• Verify no refrigerant leaks at the high pressure switch connection
• Check that compressor cycles normally and responds to AC control inputs
• Use scan tool to verify no AC-related trouble codes are present

Related trouble codes on this vehicle

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