- Boilers
- Gas boiler
F10
Saunier Duval F.10 on a gas boiler: flow sensor short circuit
Risk level
Medium
Proceed carefully and stop if the check is unclear.
Urgency
Medium
Quick answer
Saunier Duval F.10 means a short circuit in the flow temperature sensor: the board gets no valid reading from it. Take a photo of the code, press the reset key once and wait five seconds. If it stays, call the official service centre.
Safety first
Stop and check this first
- Do not open the boiler to check connectors or cables: Saunier Duval tells you never to do maintenance or repair work yourself and to leave it to a qualified installer. Inside there is mains voltage and gas parts.
- 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.
Safe checks you can perform
- Code on the display and other codes
- Recent work on the boiler
- One reset with the fault key
- Sensor and harness measured by the technician
Leave these tasks to a qualified professional
- Do not attempt this professional task: Flow NTC sensor resistance
- Do not attempt this professional task: Wiring harness between sensor and board
- Do not attempt this professional task: Fault memory and flow reading
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.
Flow NTC sensor resistance
What they doThe technician disconnects the flow temperature sensor and measures its resistance with a multimeter.
They must show youthe measured value against the manufacturer's specification.
In writingthe value and, if the sensor is replaced, its reference and why.
Wiring harness between sensor and board
What they doWith the sensor disconnected, checks that the harness wires are not short circuited to each other up to the board connector.
They must show youthe harness measurement with the sensor disconnected.
In writingwhether the harness was short circuited and what was repaired.
Fault memory and flow reading
What they doAfter the repair, reads the last 10 codes in the fault memory and checks the flow temperature in diagnostic code d.40 with the boiler running.
They must show youthe code list and the d.40 reading.
In writingthe codes found before clearing them and the test run.
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.
Code on the display and other codes
- Who:
- you.
- How:
- take a photo of the display. If several faults are present, Saunier Duval shows them alternately every two seconds: wait a few seconds and note them all.
- Result that matters:
- whether F.10 appears alone or alternates with other codes.
- If it appears alone:
- the fault is in the flow sensor or its cable; go on to the next check.
- If it alternates with others:
- note them all; if F.64 appears, which also covers a short circuit in the flow or return sensor, tell the technician.
- Evidence to keep:
- photos of the display with date and time.
Evidence: Saunier Duval ThemaFast Condens, instrucciones de funcionamiento 0020238204_00
Recent work on the boiler
- Who:
- you.
- How:
- think back to whether anyone opened the boiler recently for a service or a repair.
- Result that matters:
- whether F.10 started right after it.
- If it started after some work:
- tell the technician; ask them to check the wiring harness first where the work was done.
- If there was no work:
- the sensor or its cable may have failed on its own; the technician separates them by measuring.
- Evidence to keep:
- date and report of the last service.
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.10 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
Sensor and harness measured by the technician
- Who:
- official service centre technician or qualified installer.
- How:
- with the boiler powered off, disconnects the flow sensor, measures its resistance and checks whether the harness to the board is short circuited.
- Result that matters:
- whether the short circuit is in the sensor or in the cable.
- If the sensor reads outside the specification:
- the sensor is replaced.
- If the sensor is fine and the harness is short circuited:
- the harness is repaired or replaced, not the sensor.
- Evidence to keep:
- a report with the measured values and what was replaced.
Saunier Duval reserves inspection, maintenance, repair and gas adjustments 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
- A10 Ferroli
- Bluehelix F10
- cocina LG F10 puerta
- ecoTEC F.10
- Error F10 Ferroli
- Error F10 Saunier Duval
- Error F10 Vaillant
- F 10
- Ferroli F 10
- lavadora Miele anomalía F10
- LG F-10 horno
- LG F10 door lock
- LG F10 horno
- LG horno F10 bloqueo
- LG oven F-10
- LG oven F10 error
- LG range F10
- Miele F10 entrada de agua
- Miele F10 water inlet
- Miele lavadora F10
- Miele washer F10
- Miele washing machine fault F10
- Saunier Duval F.10
- ThemaFast Condens F.10
- Vaillant F.10
What it means
In the ThemaFast Condens table, F.10 is short circuit in the flow temperature sensor, the NTC on the heating flow. Saunier Duval gives only two causes: a faulty NTC sensor or a short circuit in the wiring harness. It is the opposite case to F.00, which flags an open circuit sensor and points mainly to loose connectors. A short circuit in the flow or return sensor is also listed among the causes of F.64, together with an electronics fault. The code does not separate the sensor from the cable.
Warnings and stop conditions
- Mediumsource verified
Do not open the boiler to check connectors or cables: Saunier Duval tells you never to do maintenance or repair work yourself and to leave it to a qualified installer. Inside there is mains voltage and gas parts.
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
Symptoms and causes
Probable causes · in order
- Faulty flow NTC sensorPossible
Saunier Duval lists it first for F.10. It is confirmed by measuring the sensor resistance, disconnected, against the manufacturer's specification.
Evidence: Saunier Duval ThemaFast Condens, instrucciones de instalación y mantenimiento 0020238203_00
- Short circuit in the wiring harnessPossible
A short circuited sensor cable gives the same code as a broken sensor. It is separated by measuring the harness between sensor and board with the sensor disconnected.
Evidence: Saunier Duval ThemaFast Condens, instrucciones de instalación y mantenimiento 0020238203_00
Virtual technician
Does F10 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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