Worcester Bosch 1037 Fault Code: Causes, Fixes & Repair Costs
What does the Worcester Bosch 1037 fault code mean?
Fault code 1037 is a blocking error on Worcester Bosch boilers that points to a problem with the flow temperature sensor or its associated wiring and connections. This sensor continuously monitors the temperature of water leaving the heat exchanger on its way around your central heating circuit. When the boiler's control system receives a reading that falls outside the expected range — or no reading at all — it triggers a temporary shutdown to prevent overheating or component damage. Because this is a blocking fault rather than a lockout, the boiler may attempt to restart automatically once the issue clears, but if the underlying problem persists the boiler will keep blocking until it is properly repaired. To see this code, you may need to press the spanner or return button on your boiler's interface, as Worcester Bosch blocking faults do not always display a code on the main screen straight away — the three-digit cause code appears when you interrogate the fault log.
General guidance only — not a substitute for professional advice. 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
- Short circuit in the flow temperature sensor (NTC thermistor) Common
The NTC thermistor is a resistive component whose electrical resistance changes predictably with temperature. If the sensor develops an internal short circuit, it sends a signal that is completely outside the permissible range, triggering the blocking fault immediately. This is the most frequently seen root cause for code 1037 and usually means the sensor itself needs replacing.
- Loose, damaged, or disconnected wiring and connector plug Common
The sensor connector can work loose over time due to vibration, or the wiring loom leading to the sensor can become chafed or corroded. If the boiler's control board receives no signal at all from the sensor, it will raise a blocking fault. An engineer will check connector seating, inspect the wire insulation, and test for continuity before condemning the sensor.
- Moisture ingress at the sensor or connector Sometimes
Condensation or a minor water leak inside the boiler casing can cause the sensor housing or its plug to become damp. This introduces unwanted resistance into the circuit and produces erratic or out-of-range temperature readings. Drying the connection may restore normal operation temporarily, but a persistent leak needs tracing and fixing.
- Incorrect sensor positioning or installation Sometimes
If the flow sensor has been disturbed during a previous service — or was incorrectly fitted at installation — it may not be making proper thermal contact with the flow pipe. This causes the boiler to see readings that don't match what the other safety sensors expect, resulting in a blocking condition.
- Faulty PCB or control unit Rare
In a small number of cases the sensor and its wiring test as perfectly healthy, yet the fault persists. This points to the control board being unable to process the sensor signal correctly. PCB faults are comparatively rare and are usually only diagnosed after all other possibilities have been eliminated by a Gas Safe engineer.
How to fix it
- Check that no other boiler faults are also present DIY safe
Before resetting, press the spanner or return button on the boiler display to read the full fault log. Note down any other codes alongside 1037, as this gives an engineer useful context if a professional visit turns out to be needed.
- Reset the boiler once or twice DIY safe
Hold the reset button for approximately three seconds (or turn the temperature dial to the reset position for three seconds, depending on your model). A single successful reset after which the boiler runs normally may indicate a transient sensor glitch. If the fault returns within a short period, do not keep resetting — further resets will not fix a genuine sensor fault and could mask important diagnostic information.
- Check your gas supply is working DIY safe
Confirm that other gas appliances in your home — such as a gas hob — are working normally. If they are not, contact your gas supplier before doing anything else. If only the boiler is affected, the issue is unlikely to be gas supply related and is almost certainly the sensor circuit.
- Visually inspect the area around the boiler for visible water leaks DIY safe
Without removing any panels, look around the base and pipework of the boiler for signs of dripping water or dried limescale deposits that might indicate a slow leak near the sensor. Report any findings to the engineer — moisture near sensors is a useful diagnostic clue.
- Do not open the boiler casing or touch internal components Gas Safe engineer
The flow temperature sensor, its wiring, and the control board are all internal components. Accessing them requires removing the boiler casing and working in close proximity to live electrical connections and the gas circuit. This work must only be carried out by a Gas Safe registered engineer. Attempting it yourself could be dangerous and will void your warranty.
- Call a Gas Safe registered engineer to diagnose and repair the fault Gas Safe engineer
An engineer will test the NTC thermistor's resistance with a multimeter (a healthy sensor follows a known resistance-versus-temperature curve), inspect the connector and wiring loom for damage or corrosion, check the sensor is correctly positioned on the flow pipe, and replace the sensor, lead, or control board as required. Always ask to see the engineer's Gas Safe ID card before work begins.
Parts you may need
- Flow temperature NTC thermistor (sensor) · from £25
- Sensor connector plug and wiring harness · from £18
- Worcester Bosch 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 £150–£280, depending on the underlying cause.
Frequently asked questions
Is fault code 1037 a lockout or a blocking fault — what is the difference?
Fault code 1037 is a blocking fault, not a lockout. A lockout means the boiler has shut down and will not restart without a manual reset. A blocking fault means the boiler has paused operation but may attempt to restart automatically once conditions return to normal. In practice, if the sensor is genuinely defective, the boiler will keep blocking repeatedly until the sensor or its wiring is repaired by a Gas Safe engineer.
Can I just reset my Worcester Bosch boiler to clear code 1037?
A reset is always worth trying once or twice — an occasional transient fault on the sensor circuit can clear itself. However, if the fault code returns soon after resetting, the underlying sensor or wiring problem is still present and resetting will not fix it. Repeatedly resetting a boiler with a genuine sensor fault can also make it harder for an engineer to diagnose the issue from the fault history.
How much does it typically cost to fix fault code 1037 in the UK?
For most homeowners, the repair involves replacing the NTC thermistor and checking the wiring, which usually comes to around £150–£280 including parts and labour. The sensor itself is an inexpensive component (typically £15–£40 for the part), so the majority of the bill is the engineer's time. If the PCB or control board also needs replacing — which is uncommon but possible — costs can rise to £350–£500 or more, depending on the boiler model and your location. London and other major cities tend to attract higher call-out rates.
Will this fault be covered under my Worcester Bosch warranty?
Worcester Bosch boilers can carry warranties of up to ten years, provided the boiler has been serviced annually by a Gas Safe registered engineer and the warranty was registered correctly at installation. If your boiler is still within this period and the servicing record is up to date, the repair may well be covered at no cost. Check your warranty documents or contact Worcester Bosch directly before authorising any paid repair work.
How can I prevent fault code 1037 coming back after repair?
The best preventive measure is an annual boiler service by a Gas Safe registered engineer. During a service, the engineer will clean sensor contacts, check wiring integrity, and identify any moisture ingress before it causes a fault. Keeping boiler pressure within the correct range (typically 1–1.5 bar when cold) and having any minor internal leaks repaired promptly will also help protect sensors from moisture damage.