Ariston 206 Fault Code: Causes, Fixes & Repair Costs
What does the Ariston 206 fault code mean?
Fault code 206 on Ariston boilers signals that the NTC temperature sensor positioned at the solar inlet to the domestic hot water (DHW) circuit has developed a short circuit. In plain terms, the sensor is sending a zero or near-zero resistance signal to the control board, which the boiler interprets as an impossible temperature reading and raises the fault to protect the system. This code sits alongside code 205, which covers the same sensor but for a loss-of-contact (open circuit) condition rather than a short. Code 206 only appears on Ariston models plumbed into a solar thermal system — if your boiler has no solar input and you are seeing this code, suspect a wiring or PCB issue rather than a faulty solar sensor.
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
- Short-circuited NTC solar inlet sensor Common
The NTC thermistor at the solar inlet to the DHW circuit develops an internal electrical fault, causing its resistance to collapse. The control board sees an implausible signal and logs code 206. This is the most frequent root cause when the code appears on a genuinely solar-connected installation.
- Damaged or chafed sensor wiring Common
The cable running from the solar inlet sensor to the PCB can suffer from heat exposure, wear, or physical damage over time. A chafed or pinched wire creating a short to earth will produce exactly the same signal as a failed sensor, and the boiler cannot distinguish between the two without physical inspection.
- Corroded or poorly seated wiring connections Sometimes
Connector blocks and terminals in the sensor circuit can corrode or work loose — particularly in installations where condensation or damp is present near the solar connections. A corroded connector can create a low-resistance path that mimics a short circuit.
- PCB fault or damaged sensor input channel Rare
If the sensor and its wiring both check out correctly, the fault may lie on the PCB itself — either a damaged input channel or a component failure on the board that misreads the sensor signal. Water ingress onto the PCB is a common trigger for this type of secondary fault.
How to fix it
- Check your Ariston warranty status before spending anything DIY safe
Ariston boilers typically carry manufacturer warranties of between 2 and 12 years depending on the model and registration. If your boiler is still within warranty, contact Ariston's customer support line directly — a covered repair costs you nothing. Check your installation paperwork or the Ariston website to confirm your warranty end date.
- Reset the boiler once or twice DIY safe
Locate the reset button on your boiler's control panel (on most Ariston models it is clearly labelled, sometimes behind a small flap). Press and hold it for around 5 seconds, then allow the boiler a minute or two to restart. If the code clears and the boiler runs normally, monitor it over the next 24 hours. If code 206 returns promptly, a reset alone will not fix the underlying fault and further investigation is needed. Do not reset more than two or three times.
- Visually inspect the solar sensor wiring where accessible DIY safe
Without opening any sealed panels or touching gas components, have a look at the external wiring runs to the solar inlet sensor if they are visible. Look for obvious signs of physical damage such as crushed cables, melted insulation, or corrosion at accessible connector ends. Note anything unusual and report it to the engineer — this can speed up diagnosis significantly.
- Engineer to test the solar inlet NTC sensor resistance Gas Safe engineer
A Gas Safe registered engineer will disconnect the sensor and measure its resistance with a multimeter. A short-circuited NTC sensor will show near-zero ohms rather than the expected resistance for the ambient temperature (typically several kilohms at room temperature). This confirms whether the sensor itself or the wiring is at fault.
- Engineer to inspect and test the sensor wiring harness Gas Safe engineer
If the sensor tests within specification in isolation, the engineer will check the full wiring loom between the sensor and the PCB for shorts to earth or shorts between conductors, paying particular attention to connector blocks and any sections of cable routed near hot surfaces.
- Engineer to replace the solar inlet NTC sensor if confirmed faulty Gas Safe engineer
Ariston solar inlet NTC sensors are relatively affordable parts, typically in the £20–£60 range depending on the exact part number. Replacement is straightforward for a competent engineer and should resolve code 206 in the majority of cases.
- Engineer to inspect the PCB if the fault persists after sensor replacement Gas Safe engineer
Should the code return even with a new sensor and confirmed sound wiring, the engineer will inspect the PCB for signs of water damage, burn marks, or a failed sensor input channel. A loose PCB connector is a quick fix; a board requiring full replacement is a more significant cost — see the FAQ below for guidance on PCB pricing.
- Call a Gas Safe registered engineer if you have not already done so Gas Safe engineer
Code 206 is not a fault a homeowner can resolve beyond a reset. All sensor testing, wiring repairs, and component replacements must be carried out by a Gas Safe registered engineer. You can verify an engineer's registration at the Gas Safe Register website (gassaferegister.co.uk).
Parts you may need
- Ariston solar inlet NTC temperature sensor · from £40
- Sensor wiring harness / loom · from £35
- Connector block / terminal repair kit · from £10
- Ariston PCB (model-specific) · from £280
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 £120–£320, depending on the underlying cause.
Frequently asked questions
Is fault code 206 the same as fault code 205 on an Ariston boiler?
They affect the same component — the NTC temperature sensor at the solar inlet to the DHW circuit — but they describe opposite electrical faults. Code 205 means the sensor circuit has gone open (lost contact), while code 206 means it has short-circuited. Both require a Gas Safe engineer to diagnose and fix, and the repair process is essentially identical: test the sensor resistance, inspect the wiring, and replace whichever component has failed.
My Ariston boiler doesn't have a solar panel — why is code 206 appearing?
Code 206 should only appear on installations with a solar thermal input connected. If your boiler has no solar system, the fault most likely points to a wiring issue or a PCB fault that is incorrectly triggering the solar sensor input channel. An engineer will need to inspect the PCB and associated wiring to identify the real cause — it is unlikely to be a solar sensor fault in this scenario.
How much does it cost to fix Ariston fault code 206?
For the most common repair — replacing the short-circuited NTC sensor and any damaged wiring — expect an all-in cost of roughly £120 to £320 including parts and labour. If the fault turns out to be the PCB, the picture changes: a replacement Ariston PCB typically costs £200–£350 for the part alone, and with an hour or two of labour the total bill can reach £400–£550. Always check your warranty first, as Ariston's manufacturer warranty (2–12 years depending on model and registration) covers faults like this at no charge.
Can I keep using my boiler while fault code 206 is showing?
That depends on whether the fault is affecting heating and hot water operation or just logging a warning. In many cases an Ariston boiler will continue to provide central heating and DHW while code 206 is active, as the fault relates to the solar input sensor rather than a core combustion or safety component. However, you should still arrange for an engineer to inspect it promptly — ignoring sensor faults can mask developing wiring problems, and the boiler's solar heat recovery function will not be operating correctly while the fault is present.