- Boilers
- Gas boiler
C7
Junkers C7 on a gas boiler: fan not running or no air flow
Risk level
High
Professional inspection is recommended.
Urgency
High
Quick answer
Junkers C7 warns of a fan problem: it is not running or there is no air flow. If there is no smell of gas or fumes, check from outside that the flue terminal is clear, note the three digit number and press reset once only.
Safety first
Stop and check this first
- If you smell gas: Bosch says do not smoke or use lighters, do not operate electrical switches or use the phone or doorbell, close the gas valve at the meter or regulator, open doors and windows, warn the neighbours and leave the building. Call your gas distributor's emergency number from the street.
- If you smell flue gases: Bosch says to shut off the gas supply, open doors and windows, warn the neighbours and leave the building. Carbon monoxide has no smell; if anyone has a headache, dizziness or nausea, get outside and call for help. A CO alarm near the boiler gives early warning.
- Do not cover or seal any vents or air inlets: Bosch forbids it so the boiler can run safely. Do not touch the flue either.
Safe checks you can perform
- Gas or flue gas smell near the boiler
- Fault code and three digit number
- Flue terminal seen from outside
- One reset with the reset key
- Fan and air path by the technician
Leave these tasks to a qualified professional
- Do not attempt this professional task: Fan test from the test menu
- Do not attempt this professional task: Flue check and combustion analysis
- Do not attempt this professional task: Fan pressure test
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 test from the test menu
What they doThe technician runs test t2: the fan runs for up to 30 seconds and, if it is fine, it can be heard.
They must show youtest t2 running.
In writingthe result and, if replaced, the fan part reference.
Flue check and combustion analysis
What they doChecks the air and flue duct and, after the repair, carries out the flue gas analysis.
They must show youthe analyser printout.
In writingthe values measured against the manufacturer's specification.
Fan pressure test
What they doWith a digital manometer on the fan test point and the boiler at maximum output, compares the reading with the Bosch chart.
They must show youthe manometer reading.
In writingthe value measured against the manufacturer's specification and what was cleaned.
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.
Gas or flue gas smell near the boiler
- Who:
- you.
- How:
- walk up without pressing switches or turning lights on and notice whether there is a smell of gas or combustion fumes.
- Result that matters:
- whether there is a smell or not.
- If there is a smell:
- do not touch the boiler and follow the gas warning on this page.
- If there is no smell:
- go on to note the full code.
- Evidence to keep:
- the time and what you noticed.
Evidence: Junkers Cerapur Excellence Compact, instrucciones de uso de la caldera mural a gas de condensación
Fault code and three digit number
- Who:
- you.
- How:
- look at the display and write down C7 and the number shown below it, 214 or 217, as Bosch asks when you report a fault.
- Result that matters:
- which of the two numbers is shown.
- If 214 is shown:
- it points to the fan itself.
- If 217 is shown:
- it may be the fan or blocked air; check the terminal.
- Evidence to keep:
- a photo of the display with the code and number.
Evidence: Junkers Cerapur Excellence Compact, instrucciones de uso de la caldera mural a gas de condensación · Junkers Cerapur Excellence Compact ZWB...A..., instrucciones de instalación y manejo para el técnico (6 720 820 575)
Flue terminal seen from outside
- Who:
- you.
- How:
- from the ground or a window, without climbing ladders or touching the flue, look at the boiler's flue outlet.
- Result that matters:
- whether there are nests, leaves, ice, plastic or damage.
- If something covers the outlet:
- do not remove it yourself unless you can reach it safely; take a photo and tell the technician.
- If it looks clear:
- the fan or an internal blockage become more likely.
- Evidence to keep:
- a photo of the terminal.
Evidence: Junkers Cerapur Excellence Compact, instrucciones de uso de la caldera mural a gas de condensación
One reset with the reset key
- Who:
- you.
- How:
- press the reset key once; Bosch says Reset is shown and, if it works, the boiler returns to normal operation.
- Result that matters:
- whether it starts without C7.
- If it starts:
- note the day and time; if C7 returns another day, call the technician.
- If the code returns and the blue LED keeps flashing:
- do not keep trying; Bosch says to contact the service team.
- Evidence to keep:
- number of attempts and the result.
Evidence: Junkers Cerapur Excellence Compact, instrucciones de uso de la caldera mural a gas de condensación
Fan and air path by the technician
- Who:
- authorised technician.
- How:
- runs fan test t2, measures the fan pressure with a digital manometer at maximum output and checks the siphon, flue pipes and heat exchanger.
- Result that matters:
- whether the fan runs and whether the pressure falls in the right zone of the Bosch chart.
- If the fan cannot be heard in t2:
- a fault in the fan or its connection is confirmed.
- If it runs but the pressure is out of range:
- the blockage is in the siphon, pipes or heat exchanger.
- Evidence to keep:
- a report with test t2, the pressure measured and what was cleaned or replaced.
The fan, siphon and heat exchanger are inside the casing, in the flue gas circuit. Bosch allows this work only by an authorised company.
Evidence: Junkers Cerapur Excellence Compact ZWB...A..., instrucciones de instalación y manejo para el técnico (6 720 820 575)
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
- C07
- C 7
- C7 214
- C7 217
- Cerapur C7
- Daikin C7
- Error C7 Junkers
- Junkers C7
What it means
On the Cerapur Excellence Compact, C7 comes with two cause numbers: 214, fan problem because it is not working, and 217, no air flow after a set time because the fan is not working or the air flow is blocked. The fan pushes combustion air and flue gases through the flue. If it fails, the boiler cannot burn safely and locks out until reset is pressed. The code does not say whether the fan has failed or air is not passing a blocked flue, siphon or heat exchanger.
Warnings and stop conditions
- Criticaleditorial warning
If you smell gas: Bosch says do not smoke or use lighters, do not operate electrical switches or use the phone or doorbell, close the gas valve at the meter or regulator, open doors and windows, warn the neighbours and leave the building. Call your gas distributor's emergency number from the street.
Evidence: Junkers Cerapur Excellence Compact, instrucciones de uso de la caldera mural a gas de condensación
- Higheditorial warning
If you smell flue gases: Bosch says to shut off the gas supply, open doors and windows, warn the neighbours and leave the building. Carbon monoxide has no smell; if anyone has a headache, dizziness or nausea, get outside and call for help. A CO alarm near the boiler gives early warning.
Evidence: Junkers Cerapur Excellence Compact ZWB...A..., instrucciones de instalación y manejo para el técnico (6 720 820 575)
- Mediumsource verified
Do not cover or seal any vents or air inlets: Bosch forbids it so the boiler can run safely. Do not touch the flue either.
Evidence: Junkers Cerapur Excellence Compact, instrucciones de uso de la caldera mural a gas de condensación
Symptoms and causes
Probable causes · in order
- Fan not workingCommon
This is the cause for numbers 214 and 217. It fits if the fan cannot be heard running on a heat demand and C7 returns after every reset.
Evidence: Junkers Cerapur Excellence Compact ZWB...A..., instrucciones de instalación y manejo para el técnico (6 720 820 575)
- Air flow blockedPossible
Bosch lists it with number 217. It fits if the fan runs but the flue terminal or the air intake is covered on the outside.
Evidence: Junkers Cerapur Excellence Compact, instrucciones de uso de la caldera mural a gas de condensación · Junkers Cerapur Excellence Compact ZWB...A..., instrucciones de instalación y manejo para el técnico (6 720 820 575)
- Blocked siphon, flue pipes or heat exchangerPossible
Bosch says to check these when the fan pressure test is out of range. They restrict the air inside even when the terminal is clear.
Evidence: Junkers Cerapur Excellence Compact ZWB...A..., instrucciones de instalación y manejo para el técnico (6 720 820 575)
Virtual technician
Does C7 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 Cerapur Excellence Compact, instrucciones de uso de la caldera mural a gas de condensación
Junkers (Bosch Termotecnia) · 2019 · manual
- 2
Junkers (Bosch Termotecnia) · 2019 · manual
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