Error Codes and Solutions for Junkers Boilers and Water Heaters
Junkers heating appliances – including gas boilers and water heaters – may display various error codes that appear on the control panel. These codes are meant to inform the user of possible faults or irregularities in the system.
Below is a list of common error codes with brief explanations of what they mean and what actions can help restore proper functionality. Whether your appliance fails to start when hot water is demanded or stops during operation, interpreting the error code correctly can speed up the diagnosis. Key factors to inspect include gas supply, flue duct ventilation, and the condition of components such as fans and sensors.
| Error | Description | Solution |
|---|---|---|
| AA | Excessive temperature detected by primary circuit sensor | Check the sensor and primary circuit temperature |
| AC | Error in communication between slide-in module and Heatronic | Check the connection cable between the modules |
| AD | Hot water tank temperature sensor or its wiring is faulty | Inspect the sensor and cabling |
| B1 | Damaged coding plug | Replace or reconnect the coding plug |
| A7 | Hot water temperature sensor issue | Check NTC and wiring |
| A9 | Incorrectly installed DHW temperature sensor | Correct the installation of the sensor |
| D5 | External temperature sensor on flow line is faulty | Replace the external temperature sensor |
| E4 | Cold water temperature sensor is faulty | Check and replace the sensor if needed |
| F7 | Flame detected when burner is off | Inspect ignition system and gas valves |
| F0 | Water flow detected before start-up | Check draw-off valve and flow system |
| A3 | Draught sensor in flue interrupter is faulty | Check sensor mounted above the burner |
| A4 | Flue draught issue detected | Inspect and clean flue gas duct |
| C1 | Air pressure switch opened during operation | Check air pressure and switch function |
| C4 | Air pressure switch does not open when idle | Inspect air pressure switch operation |
| C6 | Air pressure switch does not close on startup | Check air pressure and wiring |
| CC | External temperature sensor circuit interrupted | Replace sensor or check wiring |
| D1 | Underfloor heating temperature limiter triggered | Check heating pump and system |
| E1 | Excessive hot water temperature (>85°C) | Inspect hot water temperature sensor |
| E0 | Internal control board error | Check connections, wiring, and possibly replace the board |
| E9 | Limit temperature switch in heating circuit triggered | Inspect the heating loop and limiter |
| FA | Ionization current detected after regulator start | Check ionization electrodes and ignition components |
| A2 | Flue gas temperature limiter activated | Inspect the limiter, gas valve cabling, flue system, and bleed the unit |
| A6 | Heat exchanger temperature limiter fault | Check the limiter and wiring; replace if necessary |
| C6 | Fan malfunction | Remove obstructions, check power, test externally, replace if needed |
| B3 | Condensate buildup sensor triggered | Inspect sensor and secondary heat exchanger, clean or replace |
| E2 | Flow temperature sensor faulty | Check sensor and wiring; replace if damaged |
| C8 | Fan speed too low | Adjust fan settings, check cabling, C7 sensor, or replace fan |
| CE | Temperature gradient limit exceeded | Open service valves, activate or replace pump, set proper speed |
| EA | Flame not detected | Check gas valve, ignition, electrodes, flue and gas supply system |