Navien E302: Low water pressure
E302 is listed as 'Low water pressure.' for Navien Condensing Boiler. Verify the exact model and controller before acting.
Source checked 2026-05-01Error Codes
Browse published fault-code records by brand, product and displayed code.
Each record starts with the source meaning, then separates applicability, owner-safe actions, operating uncertainty and qualified-service boundaries. A matching code string alone is not enough: confirm the brand, product, model and controller before acting.
Navien E352: High water pressure
E352 is listed as 'High water pressure.' for Navien Condensing Boiler. Verify the exact model and controller before acting.
Source checked 2026-05-01Navien E353: Abnormal operation: water pressure sensor
E353 is listed as 'Abnormal operation: water pressure sensor.' for Navien Condensing Boiler. Verify the exact model and controller before acting.
Source checked 2026-05-01Navien E480: Abnormal operation: DHW tank temperature sensor
E480 is listed as 'Abnormal operation: DHW tank temperature sensor.' for Navien Condensing Boiler. Verify the exact model and controller before acting.
Source checked 2026-05-01Navien E515: Abnormal operation: PCB component
E515 is listed as 'Abnormal operation: PCB component.' for Navien Condensing Boiler. Verify the exact model and controller before acting.
Source checked 2026-05-01Navien E517: Abnormal operation: DIP switch setting (PCB)
E517 is listed as 'Abnormal operation: DIP switch setting (PCB).' for Navien Condensing Boiler. Verify the exact model and controller before acting.
Source checked 2026-05-01Navien E594: Abnormal operation: EEPROM (PCB)
E594 is listed as 'Abnormal operation: EEPROM (PCB).' for Navien Condensing Boiler. Verify the exact model and controller before acting.
Source checked 2026-05-01Navien E615: Abnormal operation: MCU
E615 is listed as 'Abnormal operation: MCU.' for Navien Condensing Boiler. Verify the exact model and controller before acting.
Source checked 2026-05-01Navien E736: Abnormal operation: Cascade communication
E736 is listed as 'Abnormal operation: Cascade communication.' for Navien Condensing Boiler. Verify the exact model and controller before acting.
Source checked 2026-05-01Navien E740: Abnormal operation: outdoor temperature sensor
E740 is listed as 'Abnormal operation: outdoor temperature sensor.' for Navien Condensing Boiler. Verify the exact model and controller before acting.
Source checked 2026-05-01Navien E765: Abnormal external-pump
E765 is listed as 'Abnormal external-pump.' for Navien Condensing Boiler. Verify the exact model and controller before acting.
Source checked 2026-05-01Navien E774: Manual reset limit
E774 is listed as 'Manual reset limit.' for Navien Condensing Boiler. Verify the exact model and controller before acting.
Source checked 2026-05-01Navien E775: Auto reset limit
E775 is listed as 'Auto reset limit.' for Navien Condensing Boiler. Verify the exact model and controller before acting.
Source checked 2026-05-01Navien E777: Abnormal operation: LWCO limit (external device)
E777 is listed as 'Abnormal operation: LWCO limit (external device).' for Navien Condensing Boiler. Verify the exact model and controller before acting.
Source checked 2026-05-01Navien E782: Abnormal operation: boiler communication
E782 is listed as 'Abnormal operation: boiler communication.' for Navien Condensing Boiler. Verify the exact model and controller before acting.
Source checked 2026-05-01Navien E784: Abnormal operation: zone controller communication
E784 is listed as 'Abnormal operation: zone controller communication.' for Navien Condensing Boiler. Verify the exact model and controller before acting.
Source checked 2026-05-01Thermo King Alarm 118: Auto Switch from Electric to Diesel
Alarm 118 is listed as 'Auto Switch from Electric to Diesel' for Thermo King Truck/Trailer Refrigeration Unit. Verify the exact model and controller before acting.
Source checked 2026-05-01Thermo King Alarm 120: Check Alternator Excite Circuit
Alarm 120 is listed as 'Check Alternator Excite Circuit' for Thermo King Truck/Trailer Refrigeration Unit. Verify the exact model and controller before acting.
Source checked 2026-05-01Thermo King Alarm 121: Check PMW Liquid Injection Circuit
Alarm 121 is listed as 'Check PMW Liquid Injection Circuit' for Thermo King Truck/Trailer Refrigeration Unit. Verify the exact model and controller before acting.
Source checked 2026-05-01Thermo King Alarm 122: Check Diesel/Electric Circuit
Alarm 122 is listed as 'Check Diesel/Electric Circuit' for Thermo King Truck/Trailer Refrigeration Unit. Verify the exact model and controller before acting.
Source checked 2026-05-01Thermo King Alarm 123: Check Evap Coil Inlet Temp Sensor (CR)
Alarm 123 is listed as 'Check Evap Coil Inlet Temp Sensor (CR)' for Thermo King Truck/Trailer Refrigeration Unit. Verify the exact model and controller before acting.
Source checked 2026-05-01Thermo King Alarm 124: Check Evap Coil Outlet Temp Sensor (CR)
Alarm 124 is listed as 'Check Evap Coil Outlet Temp Sensor (CR)' for Thermo King Truck/Trailer Refrigeration Unit. Verify the exact model and controller before acting.
Source checked 2026-05-01Thermo King Alarm 125: Check Tank Level Sensor (CR)
Alarm 125 is listed as 'Check Tank Level Sensor (CR)' for Thermo King Truck/Trailer Refrigeration Unit. Verify the exact model and controller before acting.
Source checked 2026-05-01Thermo King Alarm 126: Check Back Pressure Regulator (CR)
Alarm 126 is listed as 'Check Back Pressure Regulator (CR)' for Thermo King Truck/Trailer Refrigeration Unit. Verify the exact model and controller before acting.
Source checked 2026-05-01