- Boilers
- Gas boiler
C6
Junkers C6 on a gas boiler: fan or air pressure switch
Risk level
High
Professional inspection is recommended.
Urgency
High
Quick answer
Junkers C6 on the CerapurComfort means the fan is not working; on older ZWE boilers, that the air pressure switch contact does not close. Either way it is a technician's job. Switch the boiler off and call the service centre.
Safety first
Stop and check this first
- If you smell gas: close the gas shut-off valve, open the windows, do not operate switches, put out any flame and, from outside the home, call the gas company and an authorised installer. If you smell flue gases: switch the boiler off, open doors and windows and call the installer.
- Bosch forbids altering parts that carry flue gases. Do not touch the flue or the pressure switch tube.
Safe checks you can perform
- Exact model on the rating plate
- Reset or power cycle
- Technician fan and pressure switch test
Leave these tasks to a qualified professional
- Do not attempt this professional task: Fan connector measurement
- Do not attempt this professional task: CO2 or O2 measurement after the repair
What a technician must be able to justify
Technician visit
These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.
These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.
Fan connector measurement
What they doThe technician measures voltage at the fan plug with a heat demand and checks the cable, as Bosch requires.
They must show youthe reading at the connector.
In writingwhat was measured and which part was replaced.
CO2 or O2 measurement after the repair
What they doAfter replacing the fan or working on the flue, the technician measures CO2 or O2 with an analyser.
They must show youthe analyser printout.
In writingthe measured values and a test with no code.
Before accepting a part or repair
Nothing has been shown yet. Do not accept a part swap based on the code alone.
Follow these steps
Note: Follow the documented order. An error code identifies the affected system, but it does not prove by itself which part has failed.
Exact model on the rating plate
- Who:
- you.
- How:
- find the model on the boiler or its rating plate (for example ZWBC or ZWE).
- Result that matters:
- whether your boiler is a CerapurComfort type condensing boiler or a ZWE with a pressure switch.
- If it is a CerapurComfort:
- C6 points to the fan.
- If it is a ZWE:
- C6 points to the air pressure switch and its path.
- Evidence to keep:
- a photo of the rating plate.
Evidence: Junkers CerapurComfort ZWBC 25-2 C, instrucciones de instalación y manejo para el técnico · Junkers ZWE 24-3 y 28-3 H A con Bosch Heatronic, instrucciones de instalación
Reset or power cycle
- Who:
- you.
- How:
- if the reset key is flashing, hold it; otherwise switch the boiler off and on, as Bosch says.
- Result that matters:
- whether the boiler starts without C6.
- If it starts:
- keep watch; if C6 returns, call the service centre.
- If C6 returns:
- do not insist; call the official service centre with the code and the appliance details.
- Evidence to keep:
- a photo of the display with C6.
Evidence: Junkers CerapurComfort ZWBC 25-2 C, instrucciones de instalación y manejo para el técnico
Technician fan and pressure switch test
- Who:
- service network gas technician.
- How:
- checks the cable, plug and fan; on a ZWE, the air path, fan, pressure switch and flue length.
- Result that matters:
- whether the fan gets power and spins, and whether the pressure switch closes.
- If the fan does not spin with power:
- that confirms the fan.
- If it spins and the switch does not close:
- it points to the switch or the flue.
- Evidence to keep:
- a report with readings and any part replaced.
The fan, pressure switch and flue are part of the combustion circuit: only the gas technician opens them.
Evidence: Junkers CerapurComfort ZWBC 25-2 C, instrucciones de instalación y manejo para el técnico · Junkers ZWE 24-3 y 28-3 H A con Bosch Heatronic, instrucciones de instalación
Still not solved
If the error persists, stop here. See what the technician must do and show you.
Where this code applies
A code is meaningful only inside the right product and version context.
Primary scope
- System
- Boilers
- Brand
- Junkers
- Product type
- Gas boiler
Known code variants
- AEG asciugatrice C6
- AEG C6 error
- AEG dryer C6
- AEG Fehler C6
- AEG secadora C6
- AEG sèche-linge C6
- AEG Trockner C6
- Bosch C6 caldera
- C06
- C-6
- C6 AEG asciugatrice
- C6 AEG dryer
- C6 AEG secadora
- C6 AEG sèche-linge
- C6 AEG Trockner
- C6 Worcester
- Cerapur C6
- code erreur AEG C6
- error AEG C6
- Error C6 Junkers
- errore AEG C6
- Greenstar C6
- Junkers C6
- Worcester boiler C6 fault
- Worcester Bosch C6
- Worcester C6
What it means
What C6 means depends on the model. On the CerapurComfort condensing boiler it is "the fan is not working", and Bosch says to check the cable, plug and fan. On the ZWE with Heatronic it is "the pressure switch contact does not close", meaning the control cannot confirm the air draught. Both watch the flue. The code does not say whether the fan, its connection, the pressure switch or the flue is at fault.
Warnings and stop conditions
- Criticalsource verified
If you smell gas: close the gas shut-off valve, open the windows, do not operate switches, put out any flame and, from outside the home, call the gas company and an authorised installer. If you smell flue gases: switch the boiler off, open doors and windows and call the installer.
Evidence: Junkers CerapurComfort ZWBC 25-2 C, instrucciones de instalación y manejo para el técnico · Junkers ZWE 24-3 y 28-3 H A con Bosch Heatronic, instrucciones de instalación
- Highsource verified
Bosch forbids altering parts that carry flue gases. Do not touch the flue or the pressure switch tube.
Evidence: Junkers CerapurComfort ZWBC 25-2 C, instrucciones de instalación y manejo para el técnico
Symptoms and causes
Probable causes · in order
- Faulty fanCommon
On the CerapurComfort it is the condition Bosch names. If the fan gets power and does not spin, it is the cause.
Evidence: Junkers CerapurComfort ZWBC 25-2 C, instrucciones de instalación y manejo para el técnico
- Fan cable or plugPossible
Bosch asks for the cable and plug to be checked before replacing the fan; a loose connector gives the same code.
Evidence: Junkers CerapurComfort ZWBC 25-2 C, instrucciones de instalación y manejo para el técnico
- Air pressure switch or duct (ZWE models)Possible
On the ZWE, C6 is the pressure switch not closing; a loose pressure switch tube or a blocked duct causes it.
Evidence: Junkers ZWE 24-3 y 28-3 H A con Bosch Heatronic, instrucciones de instalación
Virtual technician
Does C6 still appear after these checks?
Answer a few questions to narrow down the likely cause and the safest next action. Guidance only - it never replaces a professional.
Sources and technical references
- 1
Junkers CerapurComfort ZWBC 25-2 C, instrucciones de instalación y manejo para el técnico
Junkers (Bosch Termotecnia) · 2012 · manual
- 2
Junkers ZWE 24-3 y 28-3 H A con Bosch Heatronic, instrucciones de instalación
Junkers (Bosch Termotecnia) · 2000 · manual
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