A08
Brötje Flue gas sensor open/short circuit

Error A08, boiler stops, display indicates flue gas sensor fault

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Safety Warning

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.

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Possible Causes

Defective flue gas temperature sensor, Broken sensor wiring, Corroded connector at control board, Water ingress in sensor harness

How to Fix / Troubleshooting

Safety: Turn off power and allow the boiler to cool before accessing sensors.

  • 1. Locate sensor: Find the flue gas temperature sensor on the flue hood or outlet of the heat exchanger on your Brötje furnace.
  • 2. Inspect wiring: Check the cable from the sensor to the control board for cuts, crushed insulation, or signs of moisture. Dry and secure the cable away from hot surfaces.
  • 3. Check connector: Unplug and re-seat the sensor connector at both ends. Look for corrosion or bent pins.
  • 4. Resistance test: A technician can measure the sensor resistance at room temperature and compare it to Brötje specifications. Replace the sensor if out of range or intermittent.
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Repair Difficulty

Medium 3/5

Required Part

Flue Gas Sensor
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