- Boilers
- Gas boiler
F67
Vaillant F.67 on a gas boiler: implausible flame signal
Risk level
High
Professional inspection is recommended.
Urgency
High
Quick answer
Vaillant F.67 means the electronics receive a flame signal that is not plausible. If you smell gas or fumes, get out and follow the warnings. If not, take a photo of the code and call an authorised professional.
Safety first
Stop and check this first
- If you smell fumes indoors: Vaillant says to open doors and windows fully, switch the appliance off and call an authorised professional. A badly monitored flame or poor combustion can fill the home with carbon monoxide, which has no smell: if you feel headache, dizziness or nausea, ventilate, get out and call for help. A CO alarm helps.
- If you smell gas: do not operate switches, sockets, doorbells or phones, no flames or smoking, open doors and windows, close the meter valve and the appliance gas valve if you can, warn neighbours without using the bell, leave the building and call the gas company from outside. That is what Vaillant asks.
Safe checks you can perform
- Smell of gas or fumes
- Code steady or coming and going
- Flame signal check by the technician
Leave these tasks to a qualified professional
- Do not attempt this professional task: Flame signal with burner on and off
- Do not attempt this professional task: Wiring harness and flame monitor
- Do not attempt this professional task: Fault memory and combustion analysis
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.
Flame signal with burner on and off
What they doThe technician measures the flame signal while running and with the burner off, to see whether it appears when it should not.
They must show youthe signal measured against the manufacturer's specification in both states.
In writingthe values and the faulty part.
Wiring harness and flame monitor
What they doChecks the harness and connectors of the flame monitoring and the condition of the flame monitor.
They must show youthe connections and the condition of the part.
In writingwhat was repaired and, if a part is replaced, its reference.
Fault memory and combustion analysis
What they doReads the fault list and, after the repair, analyses combustion with the burner running.
They must show youthe fault list and the CO2 and CO against the manufacturer's table.
In writingthe values measured.
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.
Smell of gas or fumes
- Who:
- you.
- How:
- without any flame nearby, notice whether there is a smell of gas or fumes near the boiler.
- Result that matters:
- whether there is any smell.
- If it smells of gas:
- follow Vaillant's gas warning and leave the home.
- If it smells of fumes:
- open doors and windows, switch the appliance off and call an authorised professional.
- Evidence to keep:
- a note of the time and what you noticed.
Evidence: Vaillant ecoTEC plus VM, VMW y VMI ..6/5-5, instrucciones de funcionamiento 0020243851_02
Code steady or coming and going
- Who:
- you.
- How:
- take a photo of the display and note whether F.67 shows all the time or only now and then, and when. Vaillant says to call an authorised professional when an F.xx message appears.
- Result that matters:
- whether the fault is continuous or intermittent.
- If it is continuous:
- call the authorised professional.
- If it comes and goes:
- tell the technician; a cable that makes contact intermittently fits better than a broken part.
- Evidence to keep:
- photos of the code with date and time.
Evidence: Vaillant ecoTEC plus VMW ..6/5-5, instrucciones de instalación y mantenimiento 0020244991_01 · Vaillant ecoTEC plus VM, VMW y VMI ..6/5-5, instrucciones de funcionamiento 0020243851_02
Flame signal check by the technician
- Who:
- authorised professional.
- How:
- checks the wiring harness, the flame monitor and the circuit board, as Vaillant's table says, and measures the flame signal with the burner on and off.
- Result that matters:
- which part gives the implausible signal.
- If the wiring is damaged:
- it is repaired or replaced.
- If the wiring is fine:
- the flame monitor and the board are checked.
- Evidence to keep:
- a report of what was measured and replaced.
Vaillant reserves inspection, maintenance, repair and gas adjustments to an authorised professional: the user does not open the boiler. Flame monitoring is a gas safety device: Vaillant forbids bridging or tampering with it.
Evidence: Vaillant ecoTEC plus VMW ..6/5-5, instrucciones de instalación y mantenimiento 0020244991_01 · Vaillant ecoTEC plus VM, VMW y VMI ..6/5-5, instrucciones de funcionamiento 0020243851_02
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
- Vaillant
- Product type
- Gas boiler
Known code variants
- ecoTEC plus F.67
- Error F67 Vaillant
- F.67
- Vaillant F.67
What it means
In the ecoTEC plus VMW table, F.67 is electronics/flame fault and the cause is an implausible flame signal: what the electronics receive about the flame does not match the state of the burner. Vaillant says to check the wiring harness, the flame monitor, the device that watches the flame, and the circuit board. Without a reliable flame signal, the boiler cannot burn gas safely. The code does not say which of the three parts has failed.
Warnings and stop conditions
- Higheditorial warning
If you smell fumes indoors: Vaillant says to open doors and windows fully, switch the appliance off and call an authorised professional. A badly monitored flame or poor combustion can fill the home with carbon monoxide, which has no smell: if you feel headache, dizziness or nausea, ventilate, get out and call for help. A CO alarm helps.
Evidence: Vaillant ecoTEC plus VM, VMW y VMI ..6/5-5, instrucciones de funcionamiento 0020243851_02
- Criticalsource verified
If you smell gas: do not operate switches, sockets, doorbells or phones, no flames or smoking, open doors and windows, close the meter valve and the appliance gas valve if you can, warn neighbours without using the bell, leave the building and call the gas company from outside. That is what Vaillant asks.
Evidence: Vaillant ecoTEC plus VM, VMW y VMI ..6/5-5, instrucciones de funcionamiento 0020243851_02
Symptoms and causes
Probable causes · in order
- Damaged or loose wiring harnessPossible
Vaillant lists it first for F.67. A flame signal cable or connector in poor condition distorts it. It fits if the code comes and goes.
Evidence: Vaillant ecoTEC plus VMW ..6/5-5, instrucciones de instalación y mantenimiento 0020244991_01
- Faulty flame monitorPossible
The device that watches the flame can give a signal that does not match the burner. Only the technician can check it by measuring the signal.
Evidence: Vaillant ecoTEC plus VMW ..6/5-5, instrucciones de instalación y mantenimiento 0020244991_01
- Circuit boardPossible
If the wiring and flame monitor are fine, the board that reads the signal remains.
Evidence: Vaillant ecoTEC plus VMW ..6/5-5, instrucciones de instalación y mantenimiento 0020244991_01
Virtual technician
Does F67 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
Vaillant ecoTEC plus VMW ..6/5-5, instrucciones de instalación y mantenimiento 0020244991_01
Vaillant · 2017 · manual
- 2
Vaillant ecoTEC plus VM, VMW y VMI ..6/5-5, instrucciones de funcionamiento 0020243851_02
Vaillant · 2017 · manual
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