HVAC Error Code Lookup — Commercial
& Residential Diagnostic Database
Look up HVAC error codes and alarm diagnostics for Carrier, Trane, York, Daikin, Lennox, and Mitsubishi systems. Commercial chiller alarms, RTU fault codes, residential AC troubleshooting, OEM part numbers, and energy waste cost estimator — fix it faster, lower the electric bill.
Centrifugal Chillers
10 specification sheetsCommercial HVAC material specifications, cross-references, and insurance claim guidelines.
Carrier 19DV Chiller Alarm 104: Centrifugal Compressor Surge Diagnosis
Alarm 104 on the Carrier 19DV centrifugal chiller indicates a compressor surge condition — a...
York YK Chiller Alarm: Compressor Surge & High Lift Protection
The York YK centrifugal chiller features an advanced surge protection algorithm that monitors...
Daikin WMC Chiller Alarm E3: Motor Overcurrent & VFD Fault
Daikin WMC chillers use oil-free magnetic bearing centrifugal compressors with integrated...
Commercial Rooftop Units
10 specification sheetsCommercial HVAC material specifications, cross-references, and insurance claim guidelines.
Trane RTU Error ERR04: Evaporator Frost Protection Active
The ERR04 code on Trane Precedent and Voyager commercial rooftop units triggers when the...
Carrier WeatherExpert RTU Alarm A001: Supply Air Temperature Sensor Failure
Alarm A001 on the Carrier WeatherExpert series indicates that the supply air temperature (SAT)...
Lennox Energence RTU Alarm 27: High Pressure Cutout — Condenser Fan Failure
Alarm 27 on Lennox Energence 6-25 ton commercial rooftop units is a high-pressure cutout...
Variable Refrigerant Flow VRF
10 specification sheetsCommercial HVAC material specifications, cross-references, and insurance claim guidelines.
Daikin VRV U4 Error: Indoor-Outdoor Communication Failure
The U4 error on Daikin VRV systems indicates a communication failure on the DIII-NET bus between...
Mitsubishi City Multi Error 7100: High Pressure Protection — Outdoor Unit
Error 7100 on Mitsubishi Electric City Multi VRF systems indicates that the high-pressure sensor...
LG Multi V Error CH24: High Pressure Sensor Malfunction
Error CH24 on LG Multi V VRF systems indicates that the high-pressure sensor signal is out of...
Scroll Chillers
10 specification sheetsCommercial HVAC material specifications, cross-references, and insurance claim guidelines.
Carrier AquaSnap 30RAP Alarm 55: Low Suction Pressure — Freeze Protection
Alarm 55 on the Carrier AquaSnap 30RAP air-cooled scroll chiller indicates that the suction...
Trane CGAM Scroll Chiller Alarm LPC: Low Pressure Cutout — Circuit 1
The Low Pressure Cutout (LPC) alarm on Trane CGAM air-cooled scroll chillers protects the...
York YLAA Scroll Chiller Alarm B2: Compressor Motor Overload
Alarm B2 on the York YLAA air-cooled scroll chiller indicates that a compressor motor overload...
Why LowersHVAC?
40 Error Codes Across 6 Equipment Types
Diagnostic guides covering Carrier, Trane, York, Daikin, Lennox, Mitsubishi Electric — centrifugal chillers, RTUs, VRF systems, and scroll chillers. Each guide includes OEM part numbers, step-by-step troubleshooting, and 8+ field-verified diagnoses by James Walker, NATE-Certified Senior Commercial HVAC Service Technician.
Interactive Diagnostic Terminal
Click-to-expand troubleshooting steps built for technicians on the job. Each diagnostic procedure follows manufacturer service manual logic — verify before replacing, test before condemning. Works on your phone while you're on the roof.
Energy Waste Calculator Built In
Every error code page includes a fault-induced energy waste estimator. Calculate what that chiller alarm or RTU fault is costing in electricity — then use the OEM parts table to price the fix. Troubleshoot faster, lower the bill.