- Boilers
- Gas boiler
F68
Saunier Duval F.68 on a gas boiler: unstable flame signal
Risk level
High
Professional inspection is recommended.
Urgency
High
Quick answer
Saunier Duval F.68 means the flame signal is unstable. Check that the gas valve is open and that the condensate drain is not blocked. Press reset once; if it returns, call the official service centre and do not keep trying.
Safety first
Stop and check this first
- If you smell fumes indoors: Saunier Duval says to open doors and windows fully, switch the appliance off and call a professional. Poor combustion or fumes that do not clear properly 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: Saunier Duval says to keep away from the area, open doors and windows, light no flames and do not smoke, do not touch switches, sockets, doorbells or phones, close the meter and appliance gas valves, warn neighbours without the bell, leave the building and call the gas company from a phone outside.
- Saunier Duval warns that if the condensate siphon is empty during operation, fumes can escape into the room. If you see the drain blocked or water under the boiler, do not keep resetting and call the technician.
Safe checks you can perform
- Gas isolation valve
- Visible condensate drain
- Flue terminal from outside
- One reset with the fault key
- Gas, combustion, ionisation and flue checked by the technician
Leave these tasks to a qualified professional
- Do not attempt this professional task: Gas connection pressure at full load
- Do not attempt this professional task: Combustion analysis
- Do not attempt this professional task: Electrode, ignition cable and ionisation current
- Do not attempt this professional task: Condensate siphon and flue duct
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.
Gas connection pressure at full load
What they doThe technician measures the gas connection pressure with a manometer with the boiler at full load, as the Saunier Duval service routine requires.
They must show youthe measured pressure against the manufacturer's specification.
In writingthe value and what was corrected in the supply.
Combustion analysis
What they doConnects an analyser to the flue gas test point, runs the boiler at full load with test programme P.01 at 100, waits for a stable reading and measures CO2.
They must show youthe measured CO2 against the manufacturer's table for your gas type.
In writingthe value before and after adjustment.
Electrode, ignition cable and ionisation current
What they doChecks the ignition and flame monitoring electrode, its cable and the flame signal the board receives.
They must show youthe electrode condition and the measured signal against the manufacturer's specification.
In writingwhat was checked and, if a part is replaced, its reference and why.
Condensate siphon and flue duct
What they doChecks, cleans and fills the condensate siphon and inspects the air and flue duct for blockages or recirculation.
They must show youthe filled siphon and the duct condition.
In writingwhat was found and corrected.
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 isolation valve
- Who:
- you.
- How:
- check that the boiler gas isolation valve and the building one are open, as Saunier Duval asks. Do not touch any other part.
- Result that matters:
- whether a valve was closed or half closed.
- If it was closed or half closed:
- open it fully and go on to the reset.
- If they were open:
- the valve is ruled out; the gas pressure is measured by the technician.
- Evidence to keep:
- a photo of the valve position.
Evidence: Saunier Duval ThemaFast Condens, instrucciones de funcionamiento 0020238204_00
Visible condensate drain
- Who:
- you.
- How:
- look at the condensate drain pipe and the funnel under the boiler without taking anything apart. Saunier Duval asks you to check them for blockages.
- Result that matters:
- whether something blocks the drain or there is water under the boiler.
- If it is blocked or there is water underneath:
- stop resetting; call the official service centre and tell them.
- If it looks clear and dry:
- the visible drain is ruled out; the inner siphon is checked by the technician.
- Evidence to keep:
- photos of the drain and the floor under the boiler.
Evidence: Saunier Duval ThemaFast Condens, instrucciones de funcionamiento 0020238204_00
Flue terminal from outside
- Who:
- you.
- How:
- from the ground or a window, look at the flue terminal and the air intake. Do not climb, touch or remove anything: Saunier Duval forbids changes to the flue installation.
- Result that matters:
- whether the terminal looks covered, broken or obstructed.
- If something looks wrong:
- tell the technician; it fits fumes coming back in.
- If it looks clear:
- recirculation is not ruled out; the full check is done by the technician.
- Evidence to keep:
- a photo of the terminal from outside.
Evidence: Saunier Duval ThemaFast Condens, instrucciones de instalación y mantenimiento 0020238203_00 · Saunier Duval ThemaFast Condens, instrucciones de funcionamiento 0020238204_00
One reset with the fault key
- Who:
- you.
- How:
- press the fault clearing (reset) key and wait five seconds, as Saunier Duval describes. Do it once only.
- Result that matters:
- whether F.68 comes back.
- If it clears and stays away:
- note the date and tell the technician at the next service.
- If it persists or returns:
- do not keep resetting; call the official service centre.
- Evidence to keep:
- a photo of the display with the code and the time.
Evidence: Saunier Duval ThemaFast Condens, instrucciones de funcionamiento 0020238204_00
Gas, combustion, ionisation and flue checked by the technician
- Who:
- official service centre technician or qualified installer.
- How:
- measures the gas connection pressure at full load, analyses combustion, checks the electrode and its cable, the condensate siphon and the air and flue duct.
- Result that matters:
- which of the Saunier Duval causes is present.
- If gas pressure or CO2 are outside their specification:
- the supply or setting is corrected before replacing parts.
- If gas and combustion are fine:
- the ionisation circuit and electronics are checked.
- Evidence to keep:
- a report with gas pressure, CO2 and what was replaced.
The flame, gas, electrode and flue are gas and combustion parts. Saunier Duval reserves this work for a qualified installer: do not open the casing.
Evidence: Saunier Duval ThemaFast Condens, instrucciones de instalación y mantenimiento 0020238203_00
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
- Saunier Duval
- Product type
- Gas boiler
Known code variants
- A68
- BlueHelix Pro F68
- ecoTEC F.68
- Error F68 Saunier Duval
- Error F68 Vaillant
- F.68
- Ferroli A68
- Ferroli F68
- Saunier Duval F.68
- ThemaFast Condens F.68
- Vaillant F.68
What it means
In the ThemaFast Condens table, F.68 is flame signal fault (unstable). The board monitors the flame through the ignition and flame monitoring electrode. Saunier Duval gives as causes air in the gas, insufficient gas flow pressure, wrong excess air factor, blocked condensate pipe, wrong burner nozzle, broken ionisation current (ignition cable or electrode), flue gas recirculation and an electronics fault. The code does not say which of them is acting.
Warnings and stop conditions
- Higheditorial warning
If you smell fumes indoors: Saunier Duval says to open doors and windows fully, switch the appliance off and call a professional. Poor combustion or fumes that do not clear properly 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: Saunier Duval ThemaFast Condens, instrucciones de funcionamiento 0020238204_00
- Criticalsource verified
If you smell gas: Saunier Duval says to keep away from the area, open doors and windows, light no flames and do not smoke, do not touch switches, sockets, doorbells or phones, close the meter and appliance gas valves, warn neighbours without the bell, leave the building and call the gas company from a phone outside.
Evidence: Saunier Duval ThemaFast Condens, instrucciones de funcionamiento 0020238204_00
- Highsource verified
Saunier Duval warns that if the condensate siphon is empty during operation, fumes can escape into the room. If you see the drain blocked or water under the boiler, do not keep resetting and call the technician.
Evidence: Saunier Duval ThemaFast Condens, instrucciones de funcionamiento 0020238204_00
Symptoms and causes
Probable causes · in order
- Gas supply: air in the gas or low pressurePossible
It fits if the gas valve was not fully open or after work on the gas installation. The technician measures the connection pressure at full load.
Evidence: Saunier Duval ThemaFast Condens, instrucciones de instalación y mantenimiento 0020238203_00
- Blocked condensate pipePossible
Saunier Duval lists it for F.68. It fits if you see the drain blocked or water under the boiler, which it links to that blockage.
Evidence: Saunier Duval ThemaFast Condens, instrucciones de instalación y mantenimiento 0020238203_00 · Saunier Duval ThemaFast Condens, instrucciones de funcionamiento 0020238204_00
- Combustion out of adjustment: excess air or nozzlePossible
It only shows with an analyser: the technician compares CO2 with the manufacturer's table. It fits if the burner or gas setting was worked on recently.
Evidence: Saunier Duval ThemaFast Condens, instrucciones de instalación y mantenimiento 0020238203_00
- Flue gas recirculationPossible
Fumes come back in through the air intake. It is checked by inspecting the whole air and flue duct, which the technician does.
Evidence: Saunier Duval ThemaFast Condens, instrucciones de instalación y mantenimiento 0020238203_00
- Broken ionisation current or electronicsPossible
A damaged ignition cable or electrode cuts the flame signal. If everything above is fine, the electronics remain.
Evidence: Saunier Duval ThemaFast Condens, instrucciones de instalación y mantenimiento 0020238203_00
Virtual technician
Does F68 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
Saunier Duval ThemaFast Condens, instrucciones de instalación y mantenimiento 0020238203_00
Saunier Duval · 2016 · manual
- 2
Saunier Duval ThemaFast Condens, instrucciones de funcionamiento 0020238204_00
Saunier Duval · 2016 · manual
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