Remeha H.00.37 Fault Code: Causes, Fixes & Repair Costs
What does the Remeha H.00.37 fault code mean?
H.00.37 is a blocking fault (H-type) on Remeha boilers, meaning the boiler shuts down automatically but is designed to recover on its own once the underlying problem is resolved — no manual reset is required in the first instance. Repeated occurrences can escalate the fault to a lock-out (E-type), which does require a manual reset. The code points to the flow or return water temperature sensor reporting a reading that falls outside its valid range, most commonly because the sensor has developed an open circuit — either through failure of the NTC thermistor itself, a disconnected plug, or a break in the wiring between the sensor and the PCB. In Remeha's fault-code numbering system, code 37 specifically flags the return temperature sensor as defective or out of range. The adjacent code H.00.36 covers a similar condition on the second return sensor (removed or below-range), so if your display shows H.00.36 rather than H.00.37, the same diagnostic approach applies — check wiring and connectors first.
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
- Failed NTC temperature sensor Common
The NTC thermistor inside the sensor degrades over time and can fail outright, producing an infinite or wildly out-of-range resistance reading. This is the single most common reason for H.00.37 and typically requires the sensor to be replaced.
- Loose or disconnected wiring connector Common
The plug connecting the sensor to the wiring harness can work loose through vibration or previous servicing. An intermittent or fully open connection produces exactly the out-of-range signal that triggers this blocking code.
- Corroded sensor contacts Sometimes
Moisture ingress at the sensor connector causes oxidation on the pins, increasing contact resistance or breaking the circuit entirely. This is more common on older installations or in damp boiler locations such as garages or outbuildings.
- Damaged wiring harness Sometimes
Physical damage — chafing against pipework, pinching during a previous repair, or rodent damage — can break or short the cable between the sensor and the PCB, giving a false out-of-range reading.
- PCB fault Rare
In rare cases the PCB's sensor input circuit fails, causing it to misread a perfectly healthy sensor. This is usually only considered after the sensor and all wiring have been verified as good.
How to fix it
- Check the boiler display and attempt a single reset DIY safe
H.00.37 is a blocking fault, so the boiler may recover on its own. If it has not, locate the reset button on the boiler fascia and press it once. Do not reset more than two or three times in quick succession — repeated resets without fixing the root cause can escalate the fault to a full lock-out.
- Verify basic boiler health: gas supply and system pressure DIY safe
Make sure the gas supply is turned on at the meter and that other gas appliances in the property are working. Check the boiler pressure gauge — on most Remeha models it should read between 1.0 and 1.5 bar when cold. If it is below 1 bar, top up via the filling loop following the guidance in your boiler manual. These checks rule out simple causes before an engineer is called.
- Have a Gas Safe engineer inspect the return temperature sensor wiring and connectors Gas Safe engineer
An engineer will visually inspect the sensor connector for signs of corrosion, looseness, or damage, and check continuity along the wiring harness back to the PCB. Many H.00.37 faults are resolved at this stage simply by reseating a connector or replacing a short section of cable.
- Measure sensor resistance with a multimeter Gas Safe engineer
The engineer will remove the suspect sensor and measure its resistance at a known temperature. A healthy NTC thermistor reads approximately 10 kΩ at 25 °C. An open-circuit reading (displayed as OL or infinite resistance on the meter) confirms the sensor has failed and needs replacing.
- Replace the faulty temperature sensor Gas Safe engineer
If the sensor has failed, the engineer will fit a manufacturer-approved replacement NTC sensor. It is important to use the correct part for the specific Remeha model, as resistance characteristics vary. After fitting, the engineer will clear the fault code and run the boiler through a full heating cycle to confirm the sensor is reading correctly.
- Inspect and repair the wiring harness if damage is found Gas Safe engineer
If the sensor itself tests healthy, the engineer will trace the full cable run for chafing, pinching, or corrosion. Damaged sections should be repaired or the harness replaced rather than taped over, to prevent recurrence.
- If the fault persists after sensor and wiring checks, arrange PCB investigation Gas Safe engineer
A fault that remains after a confirmed-good sensor and intact wiring has been installed points toward the PCB's sensor input circuit. PCB diagnosis and replacement must be carried out by a qualified engineer. Given the cost of a PCB, ask the engineer to confirm the diagnosis before ordering parts, and consider the age of the boiler when deciding whether to repair or replace.
Parts you may need
- NTC return temperature sensor (Remeha compatible) · from £30
- NTC flow temperature sensor (Remeha compatible) · from £30
- Sensor wiring harness / loom · from £45
- Remeha PCB (model-specific) · 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–£250, depending on the underlying cause.
Frequently asked questions
Does H.00.37 mean I need to reset my Remeha boiler manually?
Not necessarily. The H prefix means this is a blocking fault, so the boiler should restart automatically once the cause clears. You can try pressing the reset button once or twice, but if the fault keeps returning you will need an engineer to investigate — repeated resets without a fix can escalate it to an E-type lock-out, which does need a manual reset every time.
What is the difference between Remeha fault codes H.00.36 and H.00.37?
Both codes relate to temperature sensor faults. H.00.36 flags an issue with the second return temperature sensor — either removed or reading below its valid range — and the first fix is to check wiring and connectors. H.00.37 points specifically to the return temperature sensor being defective or out of range, and is diagnosed in the same way: inspect connectors, test sensor resistance, and replace the sensor if it has failed. The diagnostic and repair process for both codes is essentially identical.
How much does it typically cost to fix a Remeha H.00.37 fault in the UK?
In most cases, where the fault is simply a failed NTC sensor or a loose connector, you can expect to pay between £100 and £250 all-in, covering the engineer's labour and the sensor part. If the wiring harness also needs attention, costs sit toward the higher end of that range. A PCB replacement — only needed in rare cases where the sensor and wiring are both healthy — is significantly more expensive, often £350 to £500 including fitting, and is worth weighing against the age and overall condition of the boiler.
My Remeha boiler is over 10 years old and keeps showing H.00.37 — should I repair or replace?
A one-off sensor failure on an older boiler is usually still worth fixing, as it is one of the cheaper repairs. However, if H.00.37 is recurring alongside other faults, or if your boiler is approaching or past the 15-year mark, it is worth asking the engineer for a replacement quotation at the same visit. Remeha's UK technical support line (0330 678 0140) can also advise on parts availability for older models, which becomes a factor if the boiler is beyond its supported service life.