The fan that removes flue gases and draws in fresh air is not running or not reaching the required speed.
What is error C6?
On Bosch Combi Boiler units, code C6 means fan fault. The fan that removes flue gases and draws in fresh air is not running or not reaching the required speed.
Likely causes
- Fan motor or bearing failure
- Fan connector / wiring
- Air pressure switch or board issue
Safe steps you can take
- Switch the boiler off and on again after one minute.
- If the fault persists, stop using it and call a technician.
With a fan fault flue gases are not safely removed; do not force the boiler to run.
Video guide
An editor-approved video appears here. For now you can search YouTube.
Watch on YouTubeFrequently asked questions
Is error C6 dangerous?
This fault needs a technician; stop using the unit and call for service.
Is a reset enough?
One reset clears temporary causes. If the code comes back, the real cause remains — don't keep resetting.
How much does the repair cost?
It depends on the part. After diagnosis the service sends the price to your tracking link; nothing is done without your approval.
Is the repair guaranteed?
Services on the platform write the warranty for parts and labour on the service form, which is sent to you as a PDF.
Sources: tesisat.org — Kombi arıza kodları . Code meanings can vary by model; check your user manual.