hvac

AC Low 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

Easy

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.

Replace the AC low pressure switch on the 1.5L turbo Honda Civic to restore proper AC system pressure monitoring and compressor clutch operation.

Warnings

⚠️AC system must be properly evacuated by a certified technician using recovery equipment. Venting refrigerant is illegal and environmentally harmful.

⚠Residual refrigerant pressure may remain even after recovery. Open fittings slowly and wear eye protection.

⚠Do not overtighten the pressure switch as the aluminum threads on the AC line can strip easily.

Tools required

AC refrigerant recovery machineEssential

Torque wrenchEssential

19mm wrench or socketEssential

Small flat blade screwdriver

Shop rags

AC vacuum pumpEssential

AC refrigerant scaleEssential

Safety glassesEssential

Parts

AC Low Pressure Switch × 1 — Use OEM Honda part 80440-TBA-A01 or equivalent
O-rings for AC line fittings × 2 — Use OEM specification
PAG oil × 1 — ND-11 PAG oil for Honda AC systems

Preparation

Park vehicle on level ground and engage parking brake
Allow engine and AC system to cool completely (minimum 2 hours)
Connect AC recovery machine and fully evacuate refrigerant from system following EPA guidelines
Verify system pressure is at zero before opening any fittings
Disconnect negative battery terminal to prevent accidental compressor engagement

Procedure

1
Locate AC low pressure switch
Open hood and locate the AC low pressure switch on the larger diameter aluminum AC line (suction line) near the firewall on the passenger side of the engine bay. The switch has a single electrical connector with a tab-style release.
2
Disconnect electrical connector
Press down on the connector tab while pulling the connector away from the switch body. If the connector is tight, use a small flat blade screwdriver to carefully depress the locking tab. Inspect connector terminals for corrosion or damage.
3
Remove old pressure switch
Using a 19mm wrench, carefully turn the pressure switch counterclockwise. Do not use excessive force as the aluminum AC line threads are soft. Remove the switch completely and inspect the sealing surface on the AC line port for damage or debris. Place shop rags below to catch any residual oil.
4
Prepare new switch for installation
Remove the old O-ring from the AC line port and clean the sealing surface with a lint-free shop rag. Install the new O-ring onto the new pressure switch. Apply a small amount of ND-11 PAG oil to the O-ring to aid installation and system lubrication.
5
Install new pressure switch
Thread the new pressure switch into the AC line port by hand until it seats against the O-ring. Using a torque wrench and 19mm socket, tighten the switch to 20.0 Nm (15.0 lb-ft). Do not exceed this specification.
Torque spec
AC Line Fittings20 Nm (15 lb-ft)
6
Reconnect electrical connector
Push the electrical connector onto the pressure switch until you hear and feel a positive click. Gently tug on the connector to verify it is fully locked in place.
7
Evacuate and recharge AC system
Connect AC service equipment. Vacuum the system to 500 microns or lower and hold for 30 minutes to verify no leaks. If vacuum holds, recharge the system with the correct amount of R-134a refrigerant (refer to underhood AC specification label, typically 450-480 grams for this model).
8
Reconnect battery and test system
Reconnect negative battery terminal. Start engine and turn AC to maximum cold with fan on high. Monitor system pressures with gauges. Low side pressure should be 25-35 PSI at idle with ambient temperature around 75°F. Verify compressor cycles on and off properly.

Reassembly

Ensure electrical connector is fully secured with audible click
Verify no refrigerant leaks at switch connection point using electronic leak detector or soap solution
Check that all AC service equipment is disconnected before closing hood

Verification

With engine running and AC on, verify compressor clutch engages and AC blows cold air
Use scan tool to verify no AC pressure sensor fault codes are present
Monitor AC system pressures to confirm they are within normal operating range (low side 25-35 PSI, high side 200-250 PSI at idle)
Verify pressure switch causes compressor to cycle off if low pressure drops below threshold
Check for refrigerant leaks at switch connection using leak detector after 24 hours of operation

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