Remeha E.04.07 Fault Code: Causes, Fixes & Repair Costs
What does the Remeha E.04.07 fault code mean?
The E.04.07 code is a permanent lockout fault (the 'E' prefix denotes a fault serious enough to stop the boiler entirely) that triggers when the boiler's control system detects an excessively large discrepancy between its two flow temperature sensors. These sensors sit on the supply side of the heat exchanger, continuously feeding temperature readings to the PCB. Under normal operation their readings should be very close to one another; when the difference grows beyond an acceptable threshold, the boiler concludes that at least one sensor is giving unreliable data and shuts down as a safety precaution. The most likely explanation is either a loose or corroded wiring connection to one of the sensors, or an NTC thermistor that has drifted out of calibration or failed outright. Because the boiler cannot safely regulate heat output without trustworthy temperature data, it will not restart until the underlying cause is resolved.
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
- Loose or corroded wiring connection to a flow sensor Common
The connector or wiring loom leading to one of the flow temperature sensors can work loose over time due to vibration, or the terminals can corrode in the damp environment inside the boiler casing. A poor electrical contact causes intermittent or wildly inaccurate resistance readings, which the PCB interprets as a temperature mismatch between the two sensors. This is the first thing a Gas Safe engineer will check because it is a quick and inexpensive fix if confirmed.
- Failed or drifting NTC thermistor Common
The flow temperature sensors are NTC (negative temperature coefficient) thermistors — small components whose electrical resistance changes predictably with temperature. If one thermistor ages, suffers heat stress, or develops an internal fault, its resistance output no longer accurately reflects the water temperature. The PCB then sees two very different readings from what should be two closely matched sensors and triggers E.04.07. Resistance can be verified with a multimeter by an engineer; a faulty thermistor will read well outside the expected value for a given water temperature.
- PCB fault causing misread sensor signals Rare
In a small number of cases the sensors themselves are fine but the PCB is misinterpreting the signals it receives — for example due to a damaged input channel or faulty analogue-to-digital conversion on the board. This is a less common cause and is usually only diagnosed after the wiring and sensors have been confirmed as good.
How to fix it
- Attempt a single boiler reset DIY safe
On Remeha Tzerra Ace and similar models, hold the reset button (marked 'R' with an arrow) for approximately two seconds to clear the lockout and allow the boiler to attempt a restart. If the boiler fires up and runs normally, monitor it over the next hour. If E.04.07 returns, do not keep resetting — repeated resets will not fix an underlying sensor fault and may mask important diagnostic information.
- Check the gas supply to the property is on DIY safe
Before calling an engineer, confirm your gas supply is live by checking whether other gas appliances such as a hob or gas fire work normally. If there is no gas supply to the property, contact your gas supplier rather than a boiler engineer.
- Have a Gas Safe engineer inspect the sensor wiring and connections Gas Safe engineer
A registered engineer will remove the boiler casing and carefully check the wiring harness and connectors leading to both flow temperature sensors. Loose pins, pushed-back terminals, and corroded contacts are all straightforward to rectify and can resolve the fault without the need for any new parts. This step should always be completed before replacing components.
- Have the engineer test sensor resistance with a multimeter Gas Safe engineer
If the wiring checks out, the engineer will measure the electrical resistance of each NTC thermistor at a known water temperature and compare the readings against the manufacturer's specification curve. A sensor reading significantly outside the expected range confirms it has failed and needs replacing.
- Replace the defective flow temperature sensor Gas Safe engineer
Remeha flow temperature sensors are relatively inexpensive (typically £20–£60 for the part). The engineer will drain down the relevant section of the system, remove the faulty sensor, fit the new one, refill, check for leaks, and carry out a functional test to confirm the boiler runs without returning E.04.07.
- If the fault persists after sensor replacement, have the PCB investigated Gas Safe engineer
If new sensors and sound wiring still result in E.04.07, the control board itself may be the source of the problem. PCB diagnosis and replacement is specialist work requiring a Gas Safe engineer and potentially a Remeha-trained technician. Discuss with your engineer whether repair or boiler replacement is the more cost-effective route given the boiler's age.
- Call a Gas Safe registered engineer if you have not already done so Gas Safe engineer
Because E.04.07 is a permanent lockout involving internal electrical components, this fault requires a Gas Safe registered engineer to diagnose and repair. You can find accredited engineers at the Gas Safe Register website (gassaferegister.co.uk). Always ask to see the engineer's Gas Safe ID card before work begins.
Parts you may need
- Flow temperature NTC thermistor sensor (Remeha Tzerra Ace / Avanta Ace / Calenta Ace) · from £35
- Sensor wiring harness / connector loom · from £25
- Remeha boiler PCB (control board) · 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 £100–£220, depending on the underlying cause.
Frequently asked questions
Can I fix Remeha E.04.07 myself by resetting the boiler?
A single reset is worth trying, as an occasional electronic glitch can sometimes cause a spurious lockout that clears on restart. However, if E.04.07 comes back after resetting, the boiler has detected a genuine sensor discrepancy that a reset cannot resolve. The wiring and sensors need to be physically checked and tested, which requires a Gas Safe registered engineer. Do not keep pressing reset — it will not cure the underlying fault.
How much does it cost to repair a Remeha E.04.07 fault in the UK?
For most homeowners this is one of the more affordable boiler repairs. Expect to pay roughly £100–£220 in total for a standard weekday call-out, which covers the engineer's time and the cost of a replacement sensor if one is needed. The sensor parts themselves are inexpensive, typically £20–£60. If the fault has damaged the PCB as well, a replacement board can add £200–£350 on top, though this is uncommon. Emergency or out-of-hours call-outs will naturally cost more, often £250 or above just for attendance.
What is the difference between a permanent (E) fault and a blocking (A) fault on Remeha boilers?
On Remeha boilers the fault code prefix tells you how serious the lockout is. An 'A' prefix indicates a blocking fault — the boiler has paused operation but will attempt to restart automatically once conditions return to normal, and a manual reset is not always required. An 'E' prefix, as seen with E.04.07, indicates a permanent fault — the boiler has locked out completely and will not restart on its own. You must reset it manually, and if the underlying cause has not been resolved it will lock out again immediately.
How can I prevent E.04.07 from recurring on my Remeha boiler?
An annual boiler service carried out by a Gas Safe registered engineer is the single most effective preventive measure. During a service the engineer will inspect wiring connections, check sensor readings, and identify any components that are starting to drift before they cause a lockout. Keeping the boiler casing sealed properly to reduce moisture ingress also helps protect electrical connections from corrosion. Remeha boilers are generally reliable and can last 10–15 years with regular servicing.