hvac

AC Low Pressure Switch

for 2021 Hyundai Tucson 2.5L I4 · AWD

Difficulty

Moderate

Time

30 min

Tools

Steps

This procedure covers the removal and replacement of the AC low pressure switch on a 2016-2024 Hyundai Tucson with the 2.5L I4 engine, requiring recovery and recharge of the AC refrigerant system.

Warnings

⚠️AC refrigerant must be recovered by a certified technician using approved equipment. Venting refrigerant to atmosphere is illegal and environmentally harmful.

⚠️Refrigerant can cause frostbite on contact with skin. Wear safety glasses and gloves when working with AC system.

⚠System must be properly evacuated and recharged with the correct refrigerant type and quantity as specified on the underhood label.

ℹ️Some refrigerant oil will be lost during switch replacement. Add approximately 10ml of PAG oil during reassembly.

Tools required

AC refrigerant recovery machineEssential

Torque wrench (10-30 Nm range)Essential

19mm wrench or socketEssential

Vacuum pumpEssential

AC manifold gauge setEssential

10mm socket

Ratchet and extension

Wire brush or shop towels

Safety glassesEssential

Parts

AC low pressure switch × 1 — Use OEM specification
AC line O-rings × 2 — Use OEM specification
PAG oil × 1 — Use OEM specification

Fluids

R-134a or R-1234yf refrigerant (as specified on underhood label)

Preparation

Verify the correct refrigerant type (R-134a or R-1234yf) from the underhood AC specification label
Park vehicle on level surface and engage parking brake
Allow engine to cool completely if recently operated
Open hood and ensure adequate ventilation in work area
Connect AC recovery machine and recover all refrigerant from the system per machine instructions

Procedure

1
Locate the AC low pressure switch
The low pressure switch is located on the larger diameter AC line (suction line) between the evaporator outlet and compressor inlet. On the 2.5L Tucson, this is typically on the passenger side of the engine bay near the firewall. The switch is a cylindrical component with an electrical connector on top and threaded into the AC line.
2
Disconnect electrical connector
Press the locking tab on the electrical connector and pull straight off the low pressure switch. If connector is difficult to remove, gently wiggle while pulling. Do not pull on wires.
3
Remove the low pressure switch
Using a 19mm wrench, turn the low pressure switch counterclockwise to remove it from the AC line. Note the orientation of the switch. Once loosened, unthread by hand and remove completely. A small amount of residual refrigerant oil may drip out.
4
Inspect and clean the port
Inspect the threaded port in the AC line for damage or debris. Use a clean shop towel to wipe away any old refrigerant oil or contaminants. Check the condition of the sealing surface. If threads are damaged, the AC line may need replacement.
5
Prepare the new switch
Remove the new AC low pressure switch from packaging. Check that it includes a new O-ring or install the new O-ring provided in parts kit. Lightly coat the O-ring with clean PAG oil to ease installation and ensure proper seal.
6
Install the new low pressure switch
Thread the new low pressure switch into the AC line port by hand, turning clockwise. Ensure it threads smoothly without cross-threading. Hand-tighten until the switch seats against the O-ring and resistance is felt.
Torque spec
AC Line Fittings20 Nm (15 lb-ft)
7
Torque the switch to specification
Using a torque wrench and 19mm socket or wrench, tighten the low pressure switch to 20.0 Nm (15.0 lb-ft). Do not overtighten as this can damage the threads or crack the switch body.
Torque spec
AC Line Fittings20 Nm (15 lb-ft)
8
Reconnect electrical connector
Push the electrical connector onto the new low pressure switch until it clicks into place. Verify the locking tab is fully engaged. Gently tug on connector to confirm secure connection.
9
Evacuate the AC system
Connect vacuum pump to AC system through manifold gauges. Evacuate system for minimum 30-45 minutes to remove all air and moisture. System should hold vacuum for at least 10 minutes after pump is shut off to verify no leaks.
10
Add refrigerant oil
Add approximately 10ml of the correct PAG oil specification through the low side service port to compensate for oil lost during switch replacement. Refer to underhood label for correct oil type.
11
Recharge AC system
Recharge the AC system with the correct type and quantity of refrigerant as specified on the underhood label. Most 2.5L Tucson models require between 1.3-1.5 lbs of refrigerant. Use AC machine or manifold gauges to charge slowly through low side port only.

Reassembly

Verify all electrical connections are secure and properly locked
Ensure no tools or parts are left in engine bay
Check that AC line fittings show no signs of refrigerant oil leakage

Verification

Start engine and turn AC to maximum cold setting with fan on high
Check manifold gauges: low side should read 25-45 PSI and high side 200-250 PSI at idle with ambient temperature around 75-80°F
Verify low pressure switch electrical connector for proper operation (AC compressor should cycle on/off normally)
Check for cold air from cabin vents (should be 35-45°F at vent)
Inspect all connections for refrigerant oil leaks after 5 minutes of operation
Use AC leak detector around new switch location to verify no refrigerant leaks
Confirm AC compressor clutch engages and disengages properly during operation