Remeha H.01.09 Fault Code: Causes, Fixes & Repair Costs
What does the Remeha H.01.09 fault code mean?
The H.01.09 code is a blocking fault — a temporary safety shutdown — triggered by the boiler's internal gas pressure switch (GPS). The switch has detected that gas pressure is outside the acceptable operating range, or the switch itself has developed a fault. The boiler shuts down to prevent unsafe combustion. On some Remeha Ace models (such as the Gas Ace range), this code can also appear during commissioning if optional safety components are absent but the relevant parameters are still enabled by default; in that case, a qualified engineer will need to adjust the installation parameters to match the actual components fitted.
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
- Insufficient gas supply pressure Common
The gas pressure reaching the boiler has dropped below the minimum threshold required for safe operation. This can happen if the manual gas isolation valve on the gas line isn't fully open, if there's a wider supply interruption from the network, or if neighbouring appliances are drawing heavily on the line at the same time. The GPS switch detects the shortfall and triggers the blocking fault.
- Faulty or failed gas pressure switch (GPS) Common
Over time the GPS switch can wear out, develop a stuck contact, or suffer corrosion on its electrical terminals. Even if the actual gas pressure is perfectly normal, a faulty switch will report it as out of range and cause H.01.09. This is the most common internal component failure associated with this code.
- GPS switch incorrectly fitted or wired Sometimes
If the gas pressure switch has been recently replaced or disturbed during a service, it may not be seated correctly, or its wiring connector may be loose or mismatched. An incorrect setting or poor connection can cause spurious fault signals without there being any real gas pressure problem.
- Gas valve not fully open or partially blocked Sometimes
The main gas valve — either the internal boiler valve or the external supply valve — may be partially closed, restricting flow to a level the GPS switch flags as insufficient. A sluggish or failing gas valve can produce the same symptom intermittently.
- Commissioning parameter mismatch Rare
On Remeha Gas Ace and related models, optional safety components such as the GPS switch are sometimes not fitted, yet the relevant boiler parameters remain enabled by default. If the boiler cannot detect whether the component is present or absent, H.01.09 can appear at first start-up until an engineer manually corrects the configuration.
How to fix it
- Check that other gas appliances in the home are working DIY safe
Turn on a gas hob ring or check another gas appliance. If nothing on the gas supply is working, the fault is almost certainly an interruption from your gas network provider rather than a boiler component issue. Contact your gas supplier before going any further.
- Confirm the boiler's gas isolation valve is fully open DIY safe
Locate the gas isolation valve on the pipework feeding the boiler — usually a quarter-turn lever close to the appliance. Make sure it is turned fully in line with the pipe (open position). Do not touch any internal boiler components; this check is external to the boiler casing.
- Attempt a boiler reset DIY safe
Press and hold the reset button on the boiler's control panel until the fault clears, following the sequence described in your user manual. If the fault returns within a few minutes of resetting, do not keep resetting — repeated cycling without addressing the root cause will not fix the problem and may mask it. Limit yourself to two or three attempts.
- Engineer to verify gas supply pressure at the boiler Gas Safe engineer
A Gas Safe registered engineer will connect a calibrated manometer to the gas test point and confirm that the dynamic and static supply pressures are within Remeha's specified range for the model. If pressure is low, they will investigate whether the fault lies with the meter, the supply pipework sizing, or the boiler's own gas valve.
- Engineer to inspect, test, and re-seat the GPS switch Gas Safe engineer
The engineer will check the gas pressure switch for correct mounting, inspect the wiring harness and connector for corrosion or damage, and test the switch electrically to confirm it is operating within specification. A loose or misaligned switch can be re-seated; a faulty one will be replaced.
- Engineer to replace the gas pressure switch if confirmed faulty Gas Safe engineer
If testing confirms the GPS switch has failed, the engineer will fit a replacement Remeha-compatible unit, verify the new switch is correctly set for the installation, and run a full functional test to confirm H.01.09 does not return.
- Engineer to check and correct commissioning parameters if the fault appeared at start-up Gas Safe engineer
On Gas Ace models where the GPS switch is an optional component that has not been fitted, the engineer will adjust the relevant installation parameters in the boiler's service menu so that the boiler no longer expects a signal from a switch that isn't present. This must only be done by a qualified engineer who has confirmed the component is genuinely absent.
- Call a Gas Safe registered engineer if the fault persists or you are unsure Gas Safe engineer
If the code returns after a reset, or if you were not able to identify an obvious cause such as a closed isolation valve or a network supply issue, arrange for a Gas Safe registered engineer to carry out a full inspection. Working on internal gas components without Gas Safe registration is illegal and dangerous.
Parts you may need
- Remeha Gas Pressure Switch (GPS) · from £55
- Gas valve assembly (Remeha compatible) · from £120
- Wiring harness / GPS connector loom · from £25
- Boiler PCB / control board · from £220
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 £150–£300, depending on the underlying cause.
Frequently asked questions
Is H.01.09 a lockout or a blocking fault — will the boiler restart on its own?
H.01.09 is classified as a blocking fault, which means the boiler enters a temporary safety shutdown rather than a hard lockout. In some cases it will attempt to restart automatically once the condition clears — for example if a momentary gas supply dip recovers. However, if the fault persists and the boiler does not restart by itself, you will need to press the reset button. If resetting does not clear it, the underlying cause must be investigated by a Gas Safe engineer.
Can I check the gas pressure myself to diagnose H.01.09?
You can perform a basic check by seeing whether other gas appliances in your home — a hob, for instance — are working normally. If they are, the gas supply to the property is likely fine and the fault is more probably the GPS switch or gas valve inside the boiler. Measuring actual gas pressure at the boiler's test point requires a calibrated manometer and must be carried out by a Gas Safe registered engineer, as it involves accessing internal gas components.
How much does it cost to replace a gas pressure switch on a Remeha boiler in the UK?
Most homeowners pay between £150 and £300 all-in for a GPS switch replacement on a Remeha boiler — this covers the engineer's call-out and labour (typically £80–£150) plus the switch itself (usually £30–£80 for the part). The job is relatively straightforward and normally takes 20–40 minutes once the engineer is on site. If the fault turns out to involve the gas valve rather than the switch, costs are typically higher — expect £200–£350 for a gas valve replacement. A PCB replacement, which is only needed in rare cases, can add a further £200–£400.
Why has H.01.09 appeared on my brand-new Remeha boiler during commissioning?
On certain Remeha Ace models, the gas pressure switch is an optional component. The boiler's software enables the GPS parameter by default, so if the switch has not been fitted the boiler cannot tell whether it is absent or simply faulty — and it triggers H.01.09 as a precaution. This is a recognised commissioning issue and the fix is straightforward: a qualified engineer adjusts the relevant installation parameter in the boiler's service menu to reflect the actual configuration. You should not attempt to change these parameters yourself.