HEX: 89 - Combustion air fan interruption

Fault Details:

The combustion air fan is interrupted or shorted to supply voltage UB.

Recommended Solution:

Electrical check of the fan motor. Remove the top cover of the heater unit and inspect the fan, check for rub marks, scratches, and if it moves freely.

Note, different models and controllers might have different fault code meanings. If you're not sure, you can contact Heatso directly.