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Variable Refrigerant Flow VRF Critical Interlock

LG Multi V Error CH24: High Pressure Sensor Malfunction

Published: 2026-05-23

🔍 Symptoms Checklist

  • ⚠️ System stops with 'CH24' on outdoor unit PCB display
  • ⚠️ Outdoor unit will not restart until error is cleared
  • ⚠️ LG AC Smart display shows sensor fault at specific outdoor unit address
  • ⚠️ Error may be steady (failed sensor) or intermittent (loose connector)

🛠️ OEM Replacement Parts

Part NameOEM Part NumberEst. Price
High Pressure Sensor (4-20mA, 0-5.0 MPa) EBG61312801 $210
Outdoor Unit Main PCB (Gen 4) EBR83257801 $1,600
Pressure Sensor Connector Harness EBR83257811 $35

📋 Interactive Diagnostic Procedure

Click each step to expand detailed diagnostic instructions. Follow in sequence — each step builds on the previous one.

1 Verify Sensor Output Signal
The LG Multi V high pressure sensor outputs a 4-20 mA current signal proportional to pressure. Disconnect the sensor signal wire from the main PCB and measure the current in series with a multimeter. At 0 PSIG: sensor outputs 4.0 mA. At 300 PSIG: ~12 mA. At 600 PSIG: ~20 mA. An output of 0 mA indicates an open circuit (failed sensor or broken wire). An output stuck at 4 mA regardless of system pressure indicates a failed sensor diaphragm. An output >22 mA indicates a short circuit.
2 Check Sensor Connector for Moisture
The pressure sensor connector on LG Multi V outdoor units is located on the compressor discharge line. Condensation from the suction line accumulator can drip onto this connector, causing corrosion and intermittent high-resistance faults. Disconnect, inspect the pins for green/white corrosion, clean with electrical contact cleaner, and apply dielectric grease before reconnecting. Re-route or insulate the suction line to prevent future condensation drips.
3 Perform Sensor Voltage Check at PCB
If current loop measurement isn't possible (sensor hardwired), measure the DC voltage at the PCB sensor input terminal. The PCB provides a 5V DC excitation voltage. With sensor connected and system at equalized pressure: voltage should read 2.0-3.0V DC. A reading of 5.0V indicates open sensor circuit. A reading of 0V indicates shorted sensor or PCB input failure. Compare against a known-good unit if uncertain about expected values.
4 Check PCB for Water Damage
LG Multi V outdoor unit PCBs are conformally coated but not waterproof. Water ingress through deteriorated cabinet seals or the top panel gasket can cause PCB corrosion that mimics sensor failure. Inspect the PCB for: white/green corrosion on solder joints, water staining on the board surface, or burned traces near the sensor input circuit. If water damage is found, replace both the PCB AND the cabinet seals — replacing only the PCB guarantees a repeat failure.

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References & Industry Standards

  • ASHRAE 15 — Safety Standard for Refrigeration Systems
  • ASHRAE 34 — Refrigerant Designation & Safety Classification
  • AHRI 550/590 — Water-Chilling & Heat Pump Packages
  • SMACNA — HVAC Duct Construction Standards
  • Manufacturer Service Manuals — Carrier, Trane, York, Daikin, Lennox