Ideal H A fault codewhat it means and how to fix it
A temporary code with two meanings. On an Isar it is low water pressure and Ideal say fill to 1 bar; on a gaugeless Mexico HE, Ideal send you to the radiator valves.
Take care
Which boiler is showing H A?
The right answer depends on what you can see. Pick the one that matches.
Choose the option on the left that matches what your appliance is doing, and the answer for that case appears here.
A wall-hung Isar, Icos or Esprit with a pressure gauge on the panel
Low water pressure. Ideal want 1 bar minimum on the gauge.
Repressurise to 1 bar with the filling loop, switch the boiler off and on, and call the installer if the pressure keeps dropping.
A floor-standing Mexico HE with no gauge on the boiler
Ideal treat it as a circulation warning and send you to the radiator valves.
Check whether every radiator has a thermostatic valve; if so, contact the installer. Any pressure gauge will be elsewhere on the system, and 1 bar cold is still the figure to look for.
What H A means
H A is the clearest case on the LED display of Ideal reusing a code. The H says it is temporary — it clears itself when the condition does, with no reset — and the A pairs it with the L A overheat, but what it reports depends on the boiler.
The Isar user guide is specific: "display shows H:A — check pressure gauge on boiler shows a minimum of 1 bar. If not, re-pressurise via the filling loop to 1 bar", turn the boiler off and on again to reset, and "if the pressure continues to drop after filling contact your installer", followed by the same radiator-valve check as L A. The Mexico HE is a floor-standing heat-only boiler with no pressure gauge or filling loop of its own, and its guide gives H A one line only: check whether all the radiators have thermostatic valves, and if so contact the installer.
Read together, the two guides show what the code really is — the boiler is not seeing the circulation it expects, and on the Isar Ideal know the usual reason is a system that has lost pressure. A Logic reports the pressure half of this as F1 and the flow half as L1 or Fd.
What causes it
| Cause | What is actually happening | How likely |
|---|---|---|
| System pressure below 1 bar (Isar) | Ideal's first instruction for the Isar. A slow leak or a tired expansion vessel takes the gauge below the point the boiler will run at. | Common |
| Every radiator valve closing (Mexico HE and Isar) | The one check both guides share. With thermostatic valves on every radiator and no bypass, there are moments when the boiler has no circuit to pump through. | Common |
| Pressure keeps falling after filling | Ideal's cue to call the installer. Water is leaving the system somewhere, and topping up only delays the next H A. | Occasional |
What to try yourself
On an Isar, Icos or Esprit, read the gauge on the boiler. Below 1 bar, open the filling loop valves until it reads 1 bar, close them, and turn the boiler off and on at its switch — that is Ideal's reset for this code.
On a Mexico HE, or on any of them if the pressure is fine, check whether every radiator has a thermostatic valve. If they all do, Ideal say to contact the installer, who may fit a bypass or leave one radiator on a manual valve.
If you have filled it and the gauge falls again within days, stop topping up and book an engineer. Ideal's guide is explicit that pressure which continues to drop after filling is an installer matter.
Get a Gas Safe registered engineer to look at your Ideal H A
We do not pass enquiries to a repair firm, so there is no form here. Find a Gas Safe registered engineer through the Gas Safe Register, and ask to see their registration card when they arrive — it is the register, not the van, that tells you they are qualified.
What it costs to fix
Typical repair cost
£0–£320
Time on site
15 minutes
Nothing to repressurise. Finding and fixing a leak £80–£150 upwards; an expansion vessel recharged or replaced £90–£320; a bypass fitted for an all-TRV system £120–£250.
Typical UK prices including parts and labour, updated September 2026. Your quote may differ.
Parts you may need
We may earn a commission if you buy a part through one of these links. It does not change what you pay, and it does not affect which parts we list.
Expansion vessel (8 litre, sealed system)
EV-8L£35–£85Plumbing merchant
Price checked 28 September 2026
Pressure relief valve, 3 bar
PRV-3B£18–£42Plumbing merchant
Price checked 28 September 2026
Own this appliance and had this code? . Nothing is published until a person has read it.
Related Ideal fault codes
- F1Get it checkedSystem pressure has dropped below the minimum the boiler will run at. Topping it back up to 1.2 bar usually clears it straight away.Related: water pressure
- L2Stop — call an engineerThe boiler failed to detect a flame during ignition and has locked out on the gas valve. Do not keep resetting it.Related: same brand
- F2Get it checkedThe flame was lost during operation. Ideal direct you to check the gas supply first, and that is genuinely the right order.Related: same brand
- L1Get it checkedThe boiler is not seeing enough water flow through it to run safely, so it has stopped. Usually a pump, an air lock, or a blocked filter.Related: same brand
- F3Get it checkedThe fan is not running at the speed the boiler expects, so it cannot confirm the flue is clearing and has stopped the burner firing.Related: same brand
- FDGet it checkedNo water flow has been detected. The pump is the prime suspect and this will become an overheat if it is left.Related: same brand
Own an Ideal boiler? Save it and its codes come first next time.
Related guides
Common questions about Ideal H A
Do I need to press reset for H A?
No. H codes are temporary and clear when the condition does. On the Isar, Ideal's instruction after filling is to switch the boiler off and on at the switch, not to hold the reset button.
Why does my Mexico HE not tell me about pressure?
Because it cannot see it. The Mexico HE is a heat-only boiler with no pressure gauge or filling loop of its own; any gauge is on the system pipework, wherever the installer put it. Ideal's guide therefore gives H A a circulation meaning on that boiler.
Which Logic code is H A?
F1 for the pressure meaning, and L1 or Fd for the circulation meaning. The Logic separates them; the LED display uses one code and leaves the boiler type to tell you which.
Technical review
Not reviewed by an engineer
No engineer has read this page. Severity follows what the manufacturer publishes, and we would rather tell you that than let a byline imply a sign-off.
Sources and how we verified this
We establish the facts from the sources below and then write the explanation ourselves. We do not copy manufacturer wording and we do not host their manuals.
- Manufacturer technical and service documentation
This page has not been reviewed by an engineer, and we would rather tell you that than imply otherwise. The severity rating follows what the manufacturer publishes: where they say isolate the appliance and call someone, so do we.