AC Pressure Sensor

This procedure covers the removal and replacement of the AC pressure sensor on the 2014-2018 Chevrolet Silverado 1500 with the 5.3L V8 EcoTec3 engine, including proper recovery and recharge of the AC system.

Warnings

Tools required

Parts

• AC pressure sensor × 1 — ACDelco 15-51579 or equivalent
• PAG oil for AC system × 1 — Use OEM specification PAG 46
• R-134a refrigerant × 1 — Approximately 1.8 lbs total system capacity

Preparation

1. Park vehicle on level surface and apply parking brake
2. Turn off engine and allow to cool completely
3. Locate the AC pressure sensor - it may be on the high-pressure line near the condenser (driver side front) or on the low-pressure line near the accumulator (passenger side firewall)
4. Have AC system professionally recovered by a certified technician or use approved recovery equipment to remove all refrigerant from the system
5. Disconnect negative battery cable and wait 2 minutes before proceeding

Procedure

1. 1

   Access the AC pressure sensor
   The sensor location varies by model year and configuration. For high-side sensors, access from above the driver side of the radiator support. For low-side sensors near the accumulator, access from the passenger side engine bay near the firewall. Remove any plastic engine covers or air intake components that block access to the sensor.
2. 2

   Disconnect the sensor electrical connector
   Press the locking tab on the electrical connector and carefully pull it straight off the AC pressure sensor. Do not pull on the wires themselves. Inspect the connector for corrosion or damage.
3. 3

   Remove the AC pressure sensor
   Using a 10mm wrench or appropriate size, carefully unscrew the AC pressure sensor from the AC line port. Turn counterclockwise to remove. Some refrigerant oil may drip out - this is normal. Have a clean rag ready to catch any residual oil.
4. 4

   Inspect the port and prepare new sensor
   Inspect the threaded port on the AC line for damage or debris. Clean the threads if necessary with a clean, lint-free cloth. Check the new AC pressure sensor to ensure it has an O-ring installed. If the O-ring is separate, install it on the sensor and apply a small amount of clean PAG 46 oil to lubricate the O-ring.
5. 5

   Install the new AC pressure sensor
   Thread the new AC pressure sensor into the AC line port by hand, turning clockwise. Ensure it threads smoothly without cross-threading. Hand-tighten until the sensor seats against the port, then use a torque wrench to tighten to specification. The sensor port uses the same torque as AC line fittings.
   Torque spec

   AC Line Fittings20 Nm (15 lb-ft)
6. 6

   Reconnect the electrical connector
   Push the electrical connector firmly onto the new AC pressure sensor until you hear or feel the locking tab click into place. Gently tug on the connector to verify it is fully seated and locked.
7. 7

   Reinstall any removed components
   Reinstall any engine covers, air intake components, or trim pieces that were removed for access. Ensure all fasteners are properly secured and no tools or parts are left in the engine bay.
8. 8

   Reconnect battery and perform system vacuum
   Reconnect the negative battery cable. Connect AC manifold gauges to the service ports. Use a vacuum pump to evacuate the AC system to at least 29 inches of mercury (inHg) vacuum. Hold vacuum for minimum 30 minutes to verify system integrity and remove moisture. If vacuum does not hold, there is a leak that must be addressed.
9. 9

   Recharge the AC system
   With the system still under vacuum, use proper refrigerant charging equipment to add the correct amount of R-134a refrigerant. Total system capacity is approximately 1.8 lbs (28-30 oz). Add refrigerant through the low-pressure port with engine running and AC on maximum cold. Monitor pressures on manifold gauges during charging process.
10. 10

    Verify system operation
    With the engine running and AC system on maximum cold, verify that the compressor engages and disengages properly. Check manifold gauge readings - typical operating pressures should be 25-45 PSI on low side and 150-250 PSI on high side at idle with ambient temperature around 70-80°F. Monitor for proper cooling from dashboard vents. Use a scan tool to verify the new AC pressure sensor is reading correctly and no diagnostic trouble codes are present.

Reassembly

1. Ensure all electrical connectors are fully seated and locked in place
2. Verify no tools or parts are left in the engine bay
3. Confirm AC system is properly charged to specification
4. Test AC operation through all modes and temperature settings

Verification

• Start the engine and turn AC to maximum cold setting
• Verify cold air is blowing from all dashboard vents within 1-2 minutes
• Listen for normal AC compressor engagement (cycling on and off is normal)
• Use a scan tool to verify AC pressure sensor readings are within normal range (typically 30-250 PSI depending on engine speed and ambient temperature)
• Check for any refrigerant leaks around the new sensor using electronic leak detector or soap solution
• Verify no AC-related diagnostic trouble codes are present in the system
• Confirm AC system maintains proper cooling during a 10-15 minute test drive

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