Bosch Flue Gas NTC Fault

Boiler shows a flue gas temperature sensor fault; may shut down to protect the appliance.

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

Possible Causes

Failed flue gas NTC, Wiring damage near hot flue components, Sensor dislodged from flue hood, PCB sensor circuit fault

Safety: Turn off power and gas. Flue components are part of the combustion circuit and must be handled carefully.

Steps:

Locate the flue gas NTC at the flue outlet or heat exchanger hood and ensure it is correctly positioned.
Inspect the cable for heat damage and reseat the connector.
Measure sensor resistance at room temperature and replace if out of spec.

If the new sensor does not resolve the issue, a Bosch engineer should check the PCB and flue system.

Hard 4/5

Flue Gas NTC Sensor

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