Remeha A.03.17 Fault Code: Causes, Fixes & Repair Costs
What does the Remeha A.03.17 fault code mean?
The A.03.17 code appears on Remeha boilers that use the structured alphanumeric fault code system — most notably the Quinta Ace range and similar newer Remeha models. The 'A' prefix denotes a Warning rather than a full blockage or lockout, meaning the boiler has detected a developing problem but is still attempting to operate. The '03' group relates to the water pressure and flow subsystem, and '.17' is the specific sub-fault indicating that system pressure has dropped towards or below the safe minimum threshold. In plain terms, the boiler's pressure sensor is telling you the water pressure is too low and, if left unaddressed, the warning will escalate to a blocking ('H') or lockout ('E') code, causing the boiler to shut down entirely. Act on this warning promptly — it is the system giving you an early chance to resolve the issue before a full breakdown occurs.
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
- Low system water pressure Common
The most common trigger for this warning. Central heating systems gradually lose water over time through micro-leaks and bleeding of radiators. If the pressure gauge shows below 1 bar, the system simply needs repressurising via the filling loop. The target operating pressure for most Remeha installations is between 1 and 2 bar, with around 1.5 bar being ideal.
- Leak somewhere in the system Common
A persistent or recurring pressure drop — where the system keeps needing to be topped up — usually points to a leak. Check radiator valves, pipe joints, the boiler body, and any visible pipework for signs of dampness, staining, or dripping. Even a slow weep will cause pressure to fall gradually over days or weeks.
- Faulty or out-of-range pressure sensor Sometimes
If the system pressure gauge reads normally but the A.03.17 warning is still displayed, the pressure sensor itself may be giving a false low reading. Sensors can fail, corrode, or become air-locked, causing the boiler to act as though pressure is insufficient even when it is not. This requires a Gas Safe engineer to test and replace if necessary.
- Clogged water filter restricting flow Sometimes
Remeha Quinta Ace and similar models are fitted with an in-line water filter. If this filter becomes blocked with debris or magnetite sludge, it can restrict water flow to the point where the boiler's low-pressure protection triggers the A.03.17 warning. Cleaning the filter is a relatively straightforward maintenance task.
- Failing circulation pump Rare
A pump that is wearing out or seizing may fail to maintain adequate circulation pressure around the system. If the pump is running but not moving water effectively, the boiler will detect insufficient flow or pressure. Pump failures are often accompanied by unusual noises or no heat reaching radiators despite the boiler firing.
How to fix it
- Check the system pressure gauge DIY safe
Locate the pressure gauge on the boiler — on most Remeha models it is visible on the front panel or display. A healthy reading is between 1 and 2 bar when the system is cold. If the needle or digital reading is below 1 bar, low pressure is almost certainly the cause of the A.03.17 warning.
- Repressurise via the filling loop if pressure is below 1 bar DIY safe
Find the filling loop — usually a braided flexible hose with one or two valves beneath or near the boiler. Slowly open the valve(s) and watch the pressure gauge rise. Stop when the pressure reaches approximately 1.5 bar. Close the valve(s) securely. Never overfill beyond 2 bar. If you are unsure how to locate the filling loop on your specific model, consult the user manual or call Remeha technical support on 0330 678 0140.
- Inspect the system for visible leaks DIY safe
Walk around the property and check all accessible radiators, towel rails, pipe joints, and the area immediately around the boiler for signs of moisture, damp patches, rust staining, or dripping water. Pay close attention to radiator valve connections and any recent plumbing work. If you find an active leak, do not simply keep topping up the pressure — the leak must be repaired.
- Clean the boiler water filter DIY safe
If pressure is adequate but the warning persists, locate the in-line water filter on the boiler's return pipework. Turn off the boiler and isolate the relevant section of pipework before carefully removing the filter cartridge. Rinse it under warm running water to clear any sediment or debris, then refit securely. Check the manufacturer guidance in your installation manual for the correct isolation procedure for your specific model.
- Reset the boiler DIY safe
Once you have repressurised the system and checked for leaks, attempt a boiler reset. Turn the boiler off, wait approximately 30 seconds, then switch it back on — or use the dedicated reset button if your model has one. If the A.03.17 warning clears and does not return within a day or two, the issue was likely a straightforward low-pressure event. If the warning returns repeatedly, there is an underlying fault that needs professional attention.
- Have a Gas Safe engineer inspect the pressure sensor and safety valve Gas Safe engineer
If the system pressure is correct but the warning persists, a Gas Safe registered engineer should test the pressure sensor to confirm it is reading accurately and check the safety relief valve is not weeping or discharging. A faulty sensor giving a false low reading will need to be replaced — this is not a homeowner task.
- Have a Gas Safe engineer test and service the circulation pump Gas Safe engineer
If there are signs of poor circulation — for example, some radiators staying cold, or the boiler cycling on and off rapidly — a Gas Safe or suitably qualified heating engineer should inspect the pump. They can test whether it is running correctly, check its wiring and speed settings, and replace it if it has failed. Pump replacement on commercial-scale units such as the Quinta Ace is a job for a professional.
- Call a Gas Safe registered engineer if the fault persists or you are unsure Gas Safe engineer
If the A.03.17 warning keeps returning after repressurisation, if you cannot identify the cause, or if any of the above checks are beyond what you are comfortable doing, contact a Gas Safe registered engineer. The warning will escalate to a blocking or lockout fault if ignored, leaving you without heating or hot water. You can verify an engineer's Gas Safe registration at gassaferegister.co.uk.
Parts you may need
- Water pressure sensor · from £45
- Filling loop assembly · from £25
- In-line water filter cartridge · from £18
- Circulation pump (Quinta Ace compatible) · from £150
- Pressure relief valve · from £30
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 £100–£400, depending on the underlying cause.
Frequently asked questions
Is the Remeha A.03.17 a lockout — will my boiler have stopped working?
No, not immediately. The 'A' prefix in A.03.17 stands for Warning in Remeha's fault code hierarchy, which sits below 'H' (Blocking) and 'E' (Lockout). At the warning stage the boiler is still attempting to operate but is alerting you to a pressure problem that needs attention. If the underlying cause is not resolved, the boiler will typically escalate to a blocking or lockout code and shut down completely, so it is important to act promptly rather than ignoring the warning.
How often should I check the pressure on a Remeha Quinta Ace?
A quick monthly check is a good habit. The pressure should sit between 1 and 2 bar when the system is cold, with 1.5 bar being the typical target. If you find yourself topping up the pressure more than once every few months, there is likely a slow leak somewhere in the system that should be investigated by a heating engineer rather than simply repressurising repeatedly.
My Remeha keeps losing pressure and showing A.03.17 — what does that mean?
Recurring pressure loss that keeps triggering the A.03.17 warning almost always points to a leak in the system. This could be a weeping radiator valve, a pinhole in pipework, a leaking pump seal, or a faulty pressure relief valve that is discharging water. Topping up the pressure will clear the warning temporarily but will not fix the root cause. A Gas Safe registered engineer should trace and repair the leak. Left unresolved, persistent pressure loss can cause corrosion damage and eventually a more serious breakdown.
Could the A.03.17 warning mean I need a new heat exchanger or PCB?
It is very unlikely. The A.03.17 code specifically relates to water pressure, so in the vast majority of cases the repair involves repressurising the system, fixing a leak, replacing a pressure sensor, or servicing the pump — all relatively modest costs typically in the £100–£400 range. A heat exchanger or PCB replacement would only become relevant if sludge damage or an electrical fault were discovered during investigation of the underlying pressure problem, and these scenarios are uncommon. If an engineer quotes for either component purely on the basis of this code, it is worth seeking a second opinion.