AC High Pressure Switch

This procedure covers replacement of the AC high pressure switch on a 2014-2018 Chevrolet Silverado 1500 with 5.3L V8 engine, including refrigerant recovery, switch removal, installation, and system recharge.

Warnings

Tools required

Parts

• AC high pressure switch × 1 — Use OEM specification
• AC line O-rings × 2 — Use OEM specification

Fluids

• R-134a refrigerant
• PAG oil (for AC system)

Preparation

1. Park vehicle on level surface and engage parking brake
2. Allow engine to cool completely if recently operated
3. Ensure AC recovery/recharge machine is properly calibrated and has adequate capacity
4. Gather new O-rings and have PAG oil ready for reassembly

Procedure

1. 1

   Recover AC refrigerant
   Connect AC recovery machine to low and high side service ports. Follow machine instructions to fully recover all refrigerant from the system. Verify system pressure reads 0 PSI on both gauges before proceeding. Record amount of refrigerant and oil removed for recharge reference.
2. 2

   Locate AC high pressure switch
   Open hood and locate the AC high pressure switch on the high pressure line near the condenser on the passenger side of the engine bay. The switch is a small electrical component threaded into the AC line with a two-wire connector.
3. 3

   Disconnect electrical connector
   Press the locking tab on the electrical connector and carefully pull straight off the high pressure switch. Do not pull on wires. Inspect connector terminals for corrosion or damage.
4. 4

   Remove high pressure switch
   Using an appropriate wrench or socket, carefully unthread the high pressure switch from the AC line fitting. Turn counterclockwise to remove. A small amount of residual oil may drain out - capture with shop towels. Inspect the sealing surface on the AC line for damage or debris.
5. 5

   Install new O-rings
   Remove old O-ring from the AC line port if present. Clean the sealing surface thoroughly. Lightly coat new O-rings with clean PAG oil and install onto the new high pressure switch threads. Ensure O-rings are properly seated in their grooves without twists or damage.
6. 6

   Install new high pressure switch
   Thread the new high pressure switch into the AC line fitting by hand, turning clockwise. Once hand-tight, use wrench to tighten to proper specification. Do not overtighten as this can damage the fitting or switch.
   Torque spec

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

   Reconnect electrical connector
   Push the electrical connector onto the new high pressure switch until it clicks into place. Verify the locking tab is fully engaged and connection is secure. Gently tug on connector to confirm it will not pull off.
8. 8

   Evacuate AC system
   Connect vacuum pump or recovery/recharge machine evacuation function to service ports. Evacuate system to achieve deep vacuum (minimum 29 inches Hg). Maintain vacuum for at least 30-45 minutes to remove all moisture and air. Monitor for vacuum hold - any loss indicates a leak that must be repaired before recharging.
9. 9

   Recharge AC system
   Using AC recharge machine, add refrigerant to system per factory specifications (typically 2.0-2.2 lbs R-134a for this model, verify on underhood label). Add appropriate amount of PAG oil if needed to compensate for oil lost during recovery. Follow machine instructions for proper charging procedure.
10. 10

    Test system operation
    Start engine and turn AC to maximum cold setting with fan on high. Allow system to run for 5 minutes. Verify compressor engages, both AC lines show appropriate temperatures (high side warm, low side cold), and high pressure switch connector remains secure. Monitor gauges for proper pressures (typically 25-45 PSI low side, 200-250 PSI high side at idle, varies with ambient temperature).

Reassembly

1. Verify all electrical connections are secure and properly locked
2. Confirm AC line fittings show no signs of leakage
3. Clean any spilled PAG oil from engine bay components

Verification

• Verify AC blows cold air from all vents with consistent temperature
• Check for refrigerant leaks at high pressure switch connection using leak detector or soap solution
• Confirm high and low side pressures are within specification using AC gauges
• Verify compressor cycles on and off normally as controlled by high pressure switch
• Test AC operation in various modes and fan speeds to ensure proper function

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