Any equipment can break. The main thing is to quickly and effectively eliminate the breakdown. To facilitate the task, the Bosch gas boiler gives errors on the display. These symbols indicate the cause of the malfunction. You just have to find the decryption and start looking for the problem. And we will describe the ways to eliminate it below.
Features of the Bosch gas boiler
The double-circuit device is the most popular among users. It simultaneously works for hot water supply (DHW) and heating. Some models are equipped with two heat exchangers, which ensure uninterrupted operation of the system.
Power controls are located on the control panel. Therefore, heating can be adjusted to the area of the room. How does equipment switch from one circuit to another? For this, a three-way valve is provided. The operation of the boiler is focused on the main circuit – heating. When the mixer is opened, the valve switches the flow to the DHW system.
The circulation of the coolant is provided by the pump. Sensors control the device and, in case of deviations in operation, give a signal to the control module. As a result, error codes appear.
Errors and malfunctions
The table contains error codes that correspond to the Bosch WBN 6000-24C, Bosch ZSC 24-3 (35-3) MFA, ZWC 24-3 (28-3, 35-3) MFA, Bosch ZWE 24-4 (28- 4), ZSE 24-4 MFA, Bosch ZWE 24-5 MFK, Bosch ZWE 24-4 (ZSE) MF.
| Error code | Which means | How to fix it yourself |
| A2 | The combustion chamber smokes. The heat exchanger is clogged with soot and scale. | Clean the radiator. Remove soot with a brush. Scale is removed with reagents or a solution of citric acid. |
| A3 | No signal from flue gas sensor. | Inspect the sensor wiring, tighten the contacts. Replace defective part. |
| A4 | The carbon monoxide exits the flow fuse. | Clean the pipes and chimney from clogging with soot, debris, foreign objects. Make sure you have traction. |
| A6 | There is no contact with the burner temperature sensor. | Diagnose the connections and the sensor itself. |
| A7 | The water thermistor is out of order. | |
| A8 | No contact with BUS. | Tighten the connections from the bus to the control module. Replace cable |
| A9 | Incorrect connection of the DHW temperature sensor. | Check if the connection is wrong. Install the element correctly using heat conductive paste. |
| AU | The module is not recognized. | Inspect the wiring between the module and the display, information panel. As well as connections, outdoor thermometer. |
| Ad | No connection to water heater thermistor. | Run diagnostics on all contacts, sensor. |
| b1 | The system does not find the coding plug. |
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| С1 |
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| С4 | The pressure switch does not work, does not open. | Diagnose and replace the element. When coding C6, additionally check the rotation of the fan. |
| С6 | The relay does not close. | |
| С7 | Fan defective. | Reconnect the plug, repair the fan. |
| CE | The pressure in the heating system has dropped. | Open the make-up tap. Add water until the readings are correct. |
| SS/ d5 | The system “does not see” the external temperature sensor. | Connect the cable tighter, make sure the part is working. |
| d3 | Jumper 161 on ST8 not fixed. | If the jumper is in place, connect the plug correctly. Contact the service center. |
| d4 | Temperature difference exceeded. | Conduct an inspection:
Measure pressure. |
| d7 | The control valve has failed. | Diagnose the valve, its wiring. If defective, install a new part. |
| E0 | There is a problem with the printed circuit board. | Reconnect the pins or install the work board. |
| E2 | The supply line thermistor has failed. | Make a ringing of the element for an open, short circuit. Check connectors for oxidation, clean and replace parts. |
| E9 (11) | Signal from the temperature sensor of the heat exchanger. | What to do? Check:
Clean the radiator from scale and dirt. |
| EA | Burner flame out. | How to fix the problem:
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| er | Signal about the failure of one of the nodes. | Perform a complete diagnosis of the boiler. |
| F0 | Internal problem. | Inspect and reconnect the terminals and wires to the control module. Make sure they are intact. If everything is in order, change the module. |
| F7 | The technique does not function, but the flame is detected. | Check if the flue is working properly. Confirm traction. Perform diagnostics of sensors, electrodes, cables. |
| FA | The fuel supply is shut off, but there is a signal about the presence of a flame. | Inspect the ionization electrode and the serviceability of the shut-off valves. |
| Fd | Accidental pressing of a key on the panel. | Press the same button and hold for 30 seconds. |
| | | | Fan out of adjustment. | Carry out the adjustment. |
| P | Boiler type not defined. | Establish type. |
| 23 | Fuel type specified. |
Other malfunctions
Bosch boilers have problems that are not displayed as an error.
Burner not working
It is necessary to check the status and turn on the emergency and start switches. If one of the circuit breakers is defective, repair it or replace it with a working device.
Also carry out diagnostics of temperature controllers, outlet product relays. Do a preventive cleaning of the furnace, burner, nozzles, outlet pipes.
No spark, no ignition
Look for the problem in:
- Ignition electrode. Strip it, place it closer to the burner.
- burner.
- Ignition transformer.
Noise and hum when the boiler is turned on
Clean the parts, including the heat exchanger, from scale. Salt deposits interfere with heat transfer, so the water boils and hisses. If plaque is not removed, the assembly will overheat and fail.
Hot water does not turn on
If there is no hot water when you open the faucet, inspect the three-way valve. If it breaks, it must be replaced. Also make sure that the mixer is in good condition, clean the pipes and filters from blockages.
Whistle when igniting the burner
The size of the nozzles does not correspond to the pressure in the gas line. Change them.
Black smoke and soot
The ignition unit needs to be cleaned. Parts and holes clogged with dust and dirt.
Claps, noise during ignition
What could have happened:
- Gas supply set incorrectly.
- Wrong nozzle size.
- Chimney clogged.
- Incorrect structure of the chimney shaft.
- Poor ventilation in the room.
We hope that after reading the article, you will determine the cause of the breakdown. You can do the repair yourself if you are tech savvy. However, remember: before starting work, it is necessary to turn off the gas and water supply.