Error Code 90

EC90 or Error Code 90

A 90 error code indicates a combustion abnormality. This means that the mixture of fuel and air is off from specification and is resulting in poor quality combustion.

Common issues associated with a 90 error code:

 1) Insufficient gas supply
 2) Blockage in the flue vent
 3) Debris in the fan motor
 It is recommended you contact a servicer to troubleshoot this error.

Please visit to find a local service representative.

Applicable Models

  • Models: ALL MODELS

The following video outlines some basic maintenance for a Noritz Tankless Water Heater, which may help resolve 90 error codes:

Updated on April 12, 2021

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