Question 1

What does error code EA / 6A (227) u Junkers / Buderus / Bosch mean and how to fix it?

Accepted Answer

No flame detected after ignition attempt (missing ionization current). Troubleshooting & fix: Check that the main gas shut-off valve is open, clean the condensate trap, and inspect the ignition/ionization electrode; fluctuating gas supply pressure or a faulty control board are also common causes.

Question 2

What does error code CE / H07 (1017) u Junkers / Buderus / Bosch mean and how to fix it?

Accepted Answer

Low water pressure in the heating system (below the 0.6 bar minimum threshold). Troubleshooting & fix: Refill the heating circuit via the filling loop to 1.2 – 1.5 bar; if the pressure rapidly climbs toward 3 bar when heated, the expansion vessel diaphragm has lost its air charge.

Question 3

What does error code A7 / AD u Junkers / Buderus / Bosch mean and how to fix it?

Accepted Answer

Faulty domestic hot water temperature sensor (DHW / cylinder NTC probe). Troubleshooting & fix: Broken wire or defective NTC thermistor for hot water heating in the storage tank or plate heat exchanger; measure the sensor resistance with a multimeter and replace the NTC probe.

Question 4

What does error code C6 / 3C (215) u Junkers / Buderus / Bosch mean and how to fix it?

Accepted Answer

Flue gas fan not running or air pressure switch (manostat) failed to close. Troubleshooting & fix: Differential pressure switch silicone tubes blocked by condensate, obstructed coaxial flue pipe, or worn flue fan bearings.

Question 5

What does error code E9 / D4 (224) u Junkers / Buderus / Bosch mean and how to fix it?

Accepted Answer

Heat exchanger safety temperature limiter (STB) tripped. Troubleshooting & fix: Insufficient water flow through the primary heat exchanger – verify circulation pump operation, open radiator thermostatic valves, and bleed the pump.

Junkers, Buderus & Bosch Error Codes: EA / 6A, CE / H07, A7, C6, E9 – Error Code Meaning, Troubleshooting & Repair

Error Code Reference Table for Junkers / Buderus / Bosch and step-by-step repair procedure:

Error Code	Meaning / Fault Symptom	Most Common Cause & Repair Procedure
EA / 6A (227)	No flame detected after ignition attempt (missing ionization current)	Check that the main gas shut-off valve is open, clean the condensate trap, and inspect the ignition/ionization electrode; fluctuating gas supply pressure or a faulty control board are also common causes.
CE / H07 (1017)	Low water pressure in the heating system (below the 0.6 bar minimum threshold)	Refill the heating circuit via the filling loop to 1.2 – 1.5 bar; if the pressure rapidly climbs toward 3 bar when heated, the expansion vessel diaphragm has lost its air charge.
A7 / AD	Faulty domestic hot water temperature sensor (DHW / cylinder NTC probe)	Broken wire or defective NTC thermistor for hot water heating in the storage tank or plate heat exchanger; measure the sensor resistance with a multimeter and replace the NTC probe.
C6 / 3C (215)	Flue gas fan not running or air pressure switch (manostat) failed to close	Differential pressure switch silicone tubes blocked by condensate, obstructed coaxial flue pipe, or worn flue fan bearings.
E9 / D4 (224)	Heat exchanger safety temperature limiter (STB) tripped	Insufficient water flow through the primary heat exchanger – verify circulation pump operation, open radiator thermostatic valves, and bleed the pump.