hvac

AC Low Pressure Switch

for 2021 Honda Accord 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.

This procedure replaces the AC low pressure switch on the 2018-2024 Honda Accord 1.5L Turbo, which monitors refrigerant pressure and prevents compressor operation when pressure is too low.

Warnings

⚠️AC system operates under high pressure. Always recover refrigerant with certified equipment before disconnecting any components. Releasing refrigerant into atmosphere is illegal.

⚠️Refrigerant can cause frostbite on contact with skin or eyes. Wear safety glasses and gloves during all AC work.

⚠Work on AC system only in well-ventilated area. Refrigerant displaces oxygen in confined spaces.

ℹ️This vehicle uses R-1234yf refrigerant. Do not mix with R-134a. Use only certified recovery equipment rated for R-1234yf.

Tools required

AC refrigerant recovery machineEssential

Vacuum pumpEssential

AC manifold gauge setEssential

Torque wrench (5-30 Nm range)Essential

10mm socket

Ratchet and extension

Shop towels

Safety glassesEssential

Nitrile gloves

Parts

AC low pressure switch × 1 — Use OEM specification
O-rings for AC fitting × 2 — Use OEM specification

Fluids

PAG 46 AC compressor oil — 0.1 qt
R-1234yf refrigerant

Preparation

Park vehicle on level surface and engage parking brake
Turn engine off and remove key from ignition
Allow AC system to equalize pressure for at least 10 minutes after last operation
Verify you have certified AC recovery equipment for R-1234yf refrigerant
Locate the low pressure switch on the AC suction line near the firewall on driver side

Procedure

1
Recover AC refrigerant
Connect AC recovery machine to service ports. Follow machine instructions to completely recover all R-1234yf refrigerant from the system. Wait until recovery machine indicates system is fully evacuated and no refrigerant remains. Record the amount of refrigerant recovered for recharge reference.
2
Disconnect electrical connector
Locate the low pressure switch on the larger diameter AC suction line near the firewall. Press the locking tab and disconnect the electrical connector from the switch. Move the wiring harness aside to provide clearance.
3
Remove low pressure switch
Using a 24mm wrench or adjustable wrench, turn the low pressure switch counterclockwise to unthread it from the AC line fitting. Remove the switch completely. Expect a small amount of residual refrigerant oil to drain out.
4
Inspect and clean fitting
Inspect the AC line port threads for damage or debris. Clean the fitting threads with a shop towel. Remove and discard the old O-ring from the port. Check that no debris has entered the AC line opening.
5
Install new O-ring
Install a new O-ring onto the port fitting. Lightly coat the O-ring with fresh PAG 46 compressor oil (approximately 2-3 drops) to ensure proper seal and prevent O-ring damage during installation.
6
Install new low pressure switch
Thread the new low pressure switch into the AC line fitting by hand until it seats against the O-ring. Do not cross-thread. Tighten the switch to specification using a torque wrench. The switch body itself does not use the AC Line Fittings torque spec - hand tighten firmly then add 1/4 turn.
⚠Do not overtighten the switch. Excessive torque can crack the switch housing or damage the internal pressure sensing mechanism.
7
Reconnect electrical connector
Push the electrical connector onto the low pressure switch until it clicks into place. Ensure the locking tab is fully engaged. Gently tug on the connector to verify it is secured.
8
Vacuum and leak test system
Connect vacuum pump to AC service ports. Pull vacuum on the system for minimum 30 minutes to remove all air and moisture. System should hold vacuum at -29 inHg or lower. Monitor for 10 minutes after pump shutoff - vacuum should not drop, indicating no leaks at the switch connection.
9
Recharge AC system
Using AC manifold gauges and refrigerant recovery/recharge machine, add the amount of R-1234yf refrigerant that was recovered in Step 1, or per manufacturer specification if significantly different. Start engine and turn AC to maximum cold. Monitor pressures to verify proper charge level. Low side should be 25-35 PSI at idle with AC on.

Reassembly

Verify all electrical connectors are fully secured with locking tabs engaged
Check that no tools or shop towels were left in engine compartment
Ensure AC system pressures are within normal operating range before closing hood

Verification

Start engine and turn AC system to maximum cooling
Verify compressor engages and runs continuously without cycling excessively
Check that cold air is produced from vents at normal temperature (40-50°F)
Inspect low pressure switch connection for any signs of refrigerant oil leakage
Use AC gauges to confirm low side pressure is 25-35 PSI and high side is 200-275 PSI at idle with AC on
Verify no warning lights or AC system faults are present on instrument cluster
Test that AC compressor disengages properly if refrigerant charge were to become low (switch should open circuit below approximately 25 PSI)

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