Ferroli F13 Fault Code: Causes, Fixes & Repair Costs
What does the Ferroli F13 fault code mean?
The F13 code on a Ferroli boiler indicates a problem with the heat exchanger NTC (Negative Temperature Coefficient) temperature probe — the thermistor that monitors the temperature of the heat exchanger and feeds that data back to the PCB. When the PCB receives an invalid, out-of-range, or absent signal from this sensor, it triggers F13 and shuts the boiler down as a precaution. On certain Ferroli model variants, F13 can also relate to a flue gas probe fault rather than the primary exchanger probe — the principle is the same: a sensor signal the PCB cannot trust. F13 is a blocking fault (as opposed to a lockout), meaning the boiler may recover automatically once the underlying problem is resolved, without needing a manual reset. However, if it keeps returning, professional diagnosis is needed.
General guidance only — not a substitute for professional advice, and not certified by a Gas Safe engineer. Always have your specific appliance assessed by a qualified professional. Any gas work must be carried out by a Gas Safe registered engineer. If you smell gas or suspect carbon monoxide, leave the property and call the National Gas Emergency line on 0800 111 999.
Common causes
- Failed NTC exchanger probe Common
The NTC thermistor itself has broken down internally — either an open circuit or a short circuit within the sensor element. This is the single most frequent cause of F13. Sensors degrade over time through repeated thermal cycling, and eventually the resistance readings they produce fall outside the range the PCB expects.
- Damaged or broken sensor wiring Common
The thin wires running from the probe to the PCB can become chafed, corroded, or burned — particularly if they run close to hot surfaces inside the boiler. A break or short anywhere along the cable will produce exactly the same F13 signal as a faulty sensor.
- Loose or corroded connector plugs Sometimes
Vibration from normal boiler operation can gradually work the sensor's connector plug loose from its socket on the PCB. Corrosion on the connector pins can also increase resistance in the circuit to the point where the PCB misreads the probe signal. This is a quick fix if caught early.
- PCB fault or poor PCB connection Rare
If the probe and its wiring test correctly, the issue may lie with the PCB itself — either a failed input channel or a poor solder joint that means the board cannot accurately interpret the sensor signal. PCB faults are less common but should be considered when all other components check out.
How to fix it
- Check for a one-off glitch by resetting the boiler DIY safe
Locate the reset button on your Ferroli — it is usually marked with a flame symbol or the letter R. Press and hold it for around 5–10 seconds until the boiler attempts to restart. If it runs normally and F13 does not return within a day or two, the fault may have been a temporary signal dropout. Do not reset more than two or three times; repeated resets without resolution will not fix the underlying problem and can mask a developing fault.
- Check that the boiler has adequate system pressure DIY safe
Glance at the pressure gauge on the boiler fascia. It should read between 1.0 and 1.5 bar when the system is cold. If it has dropped below 0.8 bar, top it up via the filling loop in line with your boiler's user manual. Low pressure is not a direct cause of F13 but ruling it out takes seconds and avoids an unnecessary engineer call.
- Arrange for an engineer to inspect the exchanger probe and wiring Gas Safe engineer
A Gas Safe registered engineer will use a multimeter to measure the resistance of the NTC probe at a known temperature and compare it against the manufacturer's resistance table. They will also check the full wiring loom from the probe back to the PCB for continuity, shorts, and signs of heat damage or corrosion. This step pinpoints whether the sensor, the cable, or the connector is at fault.
- Replace the faulty NTC probe if testing confirms it has failed Gas Safe engineer
If the probe resistance is outside the expected range, the engineer will fit a replacement NTC thermistor. On Ferroli boilers the sensor is typically threaded into the heat exchanger pipework and wired to the PCB via a push-fit connector, making it a straightforward swap for a competent engineer. Ferroli parts are generally reasonably priced, keeping this repair at the lower end of the cost scale.
- Have the PCB inspected or replaced if the fault persists after a new probe Gas Safe engineer
When a new probe and verified wiring do not clear F13, the engineer will turn attention to the PCB. They may test the sensor input channel directly on the board, look for damaged components, or reseat all connectors firmly. If the board is confirmed faulty, replacement is the usual outcome. Given the diagnostic complexity and the cost of a PCB, this step should only be reached after the sensor and wiring have been definitively ruled out.
- Call a Gas Safe registered engineer if F13 returns or has not cleared Gas Safe engineer
If the fault code is still showing after a reset or two, or keeps coming back after clearing, do not continue resetting and hoping for the best. Book a Gas Safe registered engineer to carry out a proper diagnosis. Attempting to access internal components yourself is unsafe and may invalidate any remaining warranty.
Parts you may need
- Ferroli NTC exchanger temperature probe · from £18
- Sensor wiring loom / harness · from £25
- PCB connector / plug set · from £12
- Ferroli PCB (control board) · from £120
The exact spare depends on your boiler's GC number (on the data badge). Check this against the part before buying.
Typical repair cost
Expect to pay roughly £90–£200, depending on the underlying cause.
Frequently asked questions
Is Ferroli F13 dangerous — do I need to turn the boiler off immediately?
F13 is a blocking fault rather than a critical safety lockout. The boiler shuts itself down automatically as a precaution when it cannot trust the exchanger probe signal, so there is no immediate danger in the way there would be with a gas leak or carbon monoxide alarm. That said, you should not keep manually resetting the boiler to force it to run while the fault is present. Leave it off and arrange for an engineer to investigate — running a boiler without reliable temperature sensing risks overheating the heat exchanger.
Can I fix Ferroli F13 myself?
The initial reset is something any homeowner can do safely. Beyond that, diagnosing and replacing an NTC probe or any wiring inside the boiler requires the casing to be removed, which should only be done by a qualified engineer. A Gas Safe registered engineer is also required for any work on the PCB. Attempting internal repairs yourself is unsafe and could invalidate your boiler warranty or home insurance.
How much does it cost to fix F13 on a Ferroli boiler?
In most cases F13 is caused by a faulty NTC probe or wiring issue, and the total repair cost including parts and labour typically falls between £90 and £200. If the PCB turns out to be the culprit, costs can rise towards £250–£350 including parts and labour, though this is a less common outcome. Always get a written quote before work begins.
Why does my Ferroli show F13 on some models as a flue probe fault rather than an exchanger probe fault?
Ferroli produces a wide range of boilers and the exact sensor that triggers F13 can vary by model. On the Modena HE and several other units it refers specifically to the heat exchanger NTC probe. On certain other variants it is associated with the flue gas temperature probe. In both cases the underlying issue is the same: the PCB is receiving a signal it cannot interpret as valid. Your engineer will check the relevant probe for your specific model using the wiring diagram for that unit.