- Boilers
- Tankless gas water heater
F171
Vaillant F.171 on a gas water heater: fan or flue fault
Risk level
High
Professional inspection is recommended.
Urgency
High
Quick answer
F.171 on the Vaillant turboMAG plus is a fault of the fan that drives out the flue gases. It can come from a blocked air or flue duct, the fan itself or the board. Do not force it to run; call a gas technician.
Safety first
Stop and check this first
- If you smell gas while the turboMAG plus shows F.171, do not operate switches, plugs, doorbells or phones, avoid any flame, open doors and windows if you can, close the meter or main gas valve and the appliance gas tap if possible, warn neighbours without ringing, leave the building, keep others out and call the emergency services and the gas supplier emergency line from outside.
- With F.171 on the turboMAG plus, if you smell fumes, a CO alarm sounds or anyone has a headache, dizziness or nausea, open doors and windows on your way out, switch the appliance off only if it is on your path, get into fresh air and call for urgent help from outside, because carbon monoxide has no smell.
Safe checks you can perform
- Deal with any fume smell first
- Note changes near the flue terminal
- One reset attempt with no smell
- Record what the display shows
Leave these tasks to a qualified professional
- Do not attempt this professional task: Inspect and clean the ducts
- Do not attempt this professional task: Diagnose fan and board
- Do not attempt this professional task: Measure CO before returning it to use
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.
Inspect and clean the ducts
What they doThe gas technician checks the air intake and flue pipes and removes any blockage.
They must show youwhat was blocking the duct, or that it was clear.
In writingthe duct condition after cleaning.
Diagnose fan and board
What they doThey test the fan and, if it is not to blame, the circuit board, replacing only the faulty part.
They must show youthe test that identifies the faulty part.
In writingwhat was replaced, fan or board.
Measure CO before returning it to use
What they doUsing test programme D.53 they measure CO at the flue sampling point; above 1500 ppm it must be corrected.
They must show youthe analyser reading at the flue sampling point.
In writingthe measured CO value and gas pressure checked.
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.
Deal with any fume smell first
If you notice a smell of fumes indoors when F.171 shows, the user manual says to open doors and windows fully, switch the appliance off and call an authorised professional. Do not draw hot water again until that inspection.
Evidence: Vaillant turboMAG plus MAG ..5/1-5 RT, instrucciones de funcionamiento 0020261985_00
Note changes near the flue terminal
Think about building work, scaffolding, awnings or any change near the turboMAG plus flue outlet since it last worked. Do not climb up or touch the terminal; just report it to the technician dealing with F.171.
Evidence: Vaillant turboMAG plus MAG ..5/1-5 RT, instrucciones de funcionamiento 0020261985_00
One reset attempt with no smell
With no fume smell or symptoms, you may apply the general method from the manual once: open and close the hot tap, switch off and on and press reset. If F.171 comes back, leave the heater switched off.
Evidence: Vaillant turboMAG plus MAG ..5/1-5 RT, instrucciones de funcionamiento 0020261985_00
Record what the display shows
Write down the code F.171, how many times it appeared and the model on the data plate on the left side. If the fan sounds different, add that to your service request.
Evidence: Vaillant turboMAG plus MAG ..5/1-5 RT, instrucciones de funcionamiento 0020261985_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
- Vaillant
- Product type
- Tankless gas water heater
Known code variants
- F.171
- turboMAG F.171
- turboMAG plus F171
- Vaillant F.171
What it means
The turboMAG plus is a room-sealed heater whose flue gases are driven out by a fan. The fault table in the installation manual links F.171 to three causes: a blocked air intake or flue pipe, which must be cleaned; a defective fan, which is replaced; and a defective circuit board. Because it concerns the exit of combustion gases, the appliance should not stay in use until a professional confirms the ducts are clear and combustion is correct.
Warnings and stop conditions
- Criticaleditorial warning
If you smell gas while the turboMAG plus shows F.171, do not operate switches, plugs, doorbells or phones, avoid any flame, open doors and windows if you can, close the meter or main gas valve and the appliance gas tap if possible, warn neighbours without ringing, leave the building, keep others out and call the emergency services and the gas supplier emergency line from outside.
Evidence: Vaillant turboMAG plus MAG ..5/1-5 RT, instrucciones de funcionamiento 0020261985_00
- Criticaleditorial warning
With F.171 on the turboMAG plus, if you smell fumes, a CO alarm sounds or anyone has a headache, dizziness or nausea, open doors and windows on your way out, switch the appliance off only if it is on your path, get into fresh air and call for urgent help from outside, because carbon monoxide has no smell.
Evidence: Vaillant turboMAG plus MAG ..5/1-5 RT, instrucciones de funcionamiento 0020261985_00
Symptoms and causes
Probable causes · in order
- Blocked air or flue pipeCommon
The combustion air intake or flue gas pipe may be blocked; the manufacturer remedy is to clean it.
Evidence: Vaillant turboMAG plus MAG ..5/1-5 RT, instrucciones de instalación y mantenimiento 0020261986_00
- Failed fanPossible
A defective fan cannot keep the flue gases moving and the table says to replace it.
Evidence: Vaillant turboMAG plus MAG ..5/1-5 RT, instrucciones de instalación y mantenimiento 0020261986_00
- Fan control board faultLess common
If ducts and fan are sound, the board that drives the fan may be responsible and is replaced.
Evidence: Vaillant turboMAG plus MAG ..5/1-5 RT, instrucciones de instalación y mantenimiento 0020261986_00
Virtual technician
Does F171 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
- 2
Vaillant turboMAG plus MAG ..5/1-5 RT, instrucciones de funcionamiento 0020261985_00
Vaillant · 2018 · manual
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