Remeha E0 Fault Code: Causes, Fixes & Repair Costs
What does the Remeha E0 fault code mean?
The E0 fault code on Remeha boilers signals that the boiler's control board has detected a problem with one or more of the water temperature sensors — specifically the flow sensor, return sensor, or the boiler body temperature sensor. These NTC thermistors continuously feed temperature data to the PCB so it can regulate how hard the burner works. When a sensor reading falls outside the expected range — due to a short circuit, open circuit, or significant drift in calibration — the boiler shuts down as a precaution to protect the heat exchanger and other internal components. Heating and hot water will both stop until the fault is cleared.
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
- Faulty or failed NTC thermistor Common
The flow or return sensor itself has deteriorated or failed outright. NTC thermistors change their electrical resistance in response to water temperature; if the component drifts badly or fails completely, the PCB sees a reading that makes no physical sense and triggers the E0 lockout. This is the single most frequent root cause.
- Loose or disconnected wiring plug Common
The sensor wiring harness can work loose over time through vibration or thermal cycling. A partially unseated connector can produce intermittent or wildly incorrect resistance readings, causing the boiler to fault even though the sensor itself is perfectly healthy. Worth checking the connector seating before condemning the sensor.
- Damaged or short-circuited sensor wiring Sometimes
Wiring that runs near hot surfaces or has been trapped during a previous service visit can develop insulation damage, leading to a short circuit between conductors. A short will drag the measured resistance to near zero, sending the PCB an impossibly high temperature signal and triggering E0.
- Low system pressure or air pocket near sensor Sometimes
If the system pressure has dropped below about 0.8 bar, or if a large air pocket is sitting around the sensor pocket, the thermistor may be measuring air rather than water temperature. This produces erratic or saturated readings and can mimic a sensor fault. Topping up the pressure and bleeding the system can clear the code in these cases.
- Sensor calibration drift Rare
Over many years of service, NTC thermistors can drift away from their original resistance curve, causing readings that are consistently inaccurate rather than outright wrong. The boiler may run intermittently before E0 becomes permanent. An engineer can confirm this by comparing the sensor's measured resistance against the manufacturer's reference table at a known water temperature.
How to fix it
- Check the system pressure gauge DIY safe
Look at the pressure gauge on the boiler front panel. It should read between 1.0 and 1.5 bar when the system is cold. If it reads below 1 bar, use the filling loop to repressurise to around 1.2–1.3 bar, then attempt a reset. Low pressure can cause spurious sensor faults.
- Reset the boiler DIY safe
Press and hold the reset button for approximately 3 seconds until the boiler attempts to restart. If E0 clears and the boiler runs normally, monitor it over the next 24–48 hours. If the fault returns promptly, further investigation by a Gas Safe engineer is needed — do not keep resetting indefinitely.
- Visually inspect accessible sensor wiring connectors DIY safe
With the boiler powered off, open the boiler casing if it lifts away easily and check whether any visible wiring plugs on the sensor leads look obviously loose, corroded, or disconnected. Do not probe, cut, or reconnect wiring — simply note what you see and report it to the engineer. Do not touch gas pipework or the PCB.
- Gas Safe engineer: test sensor resistance with a multimeter Gas Safe engineer
An engineer will disconnect the suspect sensor and measure its resistance at ambient and operating temperatures, comparing readings against the Remeha resistance-temperature table. A reading that is open-circuit, short-circuit, or significantly outside the expected range confirms the sensor needs replacing.
- Gas Safe engineer: inspect and test the wiring loom Gas Safe engineer
If the sensor resistance is within spec, the engineer will check continuity and insulation resistance along the full wiring loom from the sensor plug back to the PCB connector. Damaged or shorted cables are repaired or replaced as required.
- Gas Safe engineer: replace the faulty NTC thermistor Gas Safe engineer
Replacement Remeha-compatible NTC thermistors are widely available and relatively inexpensive. The engineer will drain the relevant section of pipework, swap the sensor, refill, repressurise, and verify the new sensor reads correctly across the operating temperature range before restoring the boiler to full service.
- If the fault persists after sensor replacement, contact a Gas Safe engineer to assess the PCB Gas Safe engineer
In rare cases where a new, correctly installed sensor still triggers E0, the fault may lie with the PCB input circuit rather than the sensor itself. PCB diagnosis and replacement is an engineer-only task.
Parts you may need
- NTC flow/return thermistor (Remeha compatible) · from £15
- Sensor wiring harness/loom · from £35
- PCB (control board) — if input circuit failed · 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 £100–£250, depending on the underlying cause.
Frequently asked questions
Can I fix a Remeha E0 fault myself?
The only safe DIY steps are checking and topping up system pressure via the filling loop, then attempting a reset. Beyond that, the fault involves testing and potentially replacing electrical sensors inside the boiler, which should be handled by a Gas Safe registered engineer. Incorrectly disturbing sensor wiring can mask a fault or create new ones.
How much does it cost to fix a Remeha E0 fault in the UK?
For a straightforward sensor replacement, most homeowners pay in the region of £100–£250 all-in, covering the engineer's call-out, labour, and the part itself (NTC thermistors typically cost £10–£30). If the wiring loom also needs replacing the cost can push toward the higher end. A PCB replacement — needed only in rare cases — adds significantly more, often £300–£500 for parts and labour, but this is uncommon for an E0 fault.
Why does my Remeha boiler show E0 intermittently rather than permanently?
An intermittent E0 usually points to a loose connector or early-stage sensor drift rather than a complete failure. As the boiler heats and cools through its cycles, the connector may make and break contact, or the sensor's resistance curve drifts in and out of acceptable limits. Intermittent faults can be harder to diagnose but are just as important to investigate, as they tend to become permanent over time.
Will topping up the pressure clear an E0 fault?
It can, but only if low pressure or an air pocket near the sensor pocket was the underlying trigger. If the system pressure was genuinely low (below 1 bar), repressurise to around 1.2 bar, bleed any radiators with trapped air, and then reset the boiler. If E0 returns within a short time, the cause is the sensor or its wiring rather than the water circuit, and an engineer's visit is needed.