hvac

AC High Pressure Switch

for 2021 Honda Civic 1.5L I4 Turbo · FWD

Editorial review:Chris Hackleman — Master Technician · 20+ years · Jeff Moore — Master Lexus & Toyota Mechanic · 20+ years

Difficulty

Moderate

Time

30 min

Tools

Steps

✓Expert-verified. Personally reviewed and approved by OLP's master technicians (Chris Hackleman & Jeff Moore — 20+ years each). Always follow the vehicle's factory service information and torque specs.

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

⚠️AC system operates under high pressure. Never disconnect lines without proper refrigerant recovery. Improper handling can cause frostbite or injury.

⚠This job requires EPA-certified AC recovery equipment and proper refrigerant handling procedures. DIY recovery is illegal in most jurisdictions.

⚠Refrigerant oil can irritate skin and eyes. Wear protective equipment throughout the procedure.

ℹ️The AC system must be evacuated and recharged after this repair. Total refrigerant capacity is approximately 16-18 oz of R-134a.

Tools required

AC recovery/evacuation/recharge machineEssential

Torque wrench (5-50 Nm range)Essential

10mm socket and ratchetEssential

12mm wrench

Flathead screwdriver or trim tool

Shop towelsEssential

Nitrile glovesEssential

Safety glassesEssential

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

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

Procedure

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
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
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
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
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
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
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
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
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
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

Ensure all electrical connectors are fully seated and locked
Verify no tools or shop towels remain in engine bay
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

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