Flow sensor damaged
The E03 error code on Ravenheat boilers indicates flow sensor damaged.
Ravenheat E03 means: flow sensor damaged. The usual causes are thermistor (ntc sensor) failure — open circuit or short circuit, loose or corroded wiring connection at the sensor or sensor out of calibration giving incorrect readings. You can safely reset the boiler once — if E03 returns, do not keep resetting. A qualified heating engineer should diagnose the root cause.
What Does E03 Mean
The E03 code is shown by the boiler’s control board when it detects flow sensor damaged. The boiler then stops instead of continuing to run in that condition: the code is the appliance reporting a problem, not proof that the boiler is broken.
| What you see on the boiler |
|---|
| The display shows E03 and the boiler stops until the fault is cleared |
Common Causes
Causes documented in 1 technical sources.
| Cause |
|---|
| Thermistor (NTC sensor) failure — open circuit or short circuit |
| loose or corroded wiring connection at the sensor |
| sensor out of calibration giving incorrect readings |
| water damage to the sensor or its wiring |
| PCB input fault — the connector on the PCB may be damaged |
Safety Warning
E03 involves electrical or pressure-related components. Do not attempt repairs without proper qualifications. Ensure the boiler is electrically isolated before any inspection. If you notice water leaks, unusual sounds, or pressure anomalies, contact a qualified heating engineer immediately.
Parts & Prices
Prices shown are indicative. Actual prices and availability vary by region.
Step-by-Step Diagnosis
Identify which sensor is faulty from the error code (flow, return, DHW, flue gas, or outdoor)
Check the wiring — inspect the connections at both the sensor and the PCB for corrosion or loose terminals
Measure the sensor resistance with a multimeter — compare with the manufacturer's resistance/temperature chart (typically 10kΩ at 25°C (77 °F) for NTC sensors)
If resistance is out of range (infinite = open circuit, near zero = short circuit), replace the sensor
If resistance is correct, check the wiring continuity between the sensor and PCB
If wiring is good, test the PCB input
How to Fix It
Replace the faulty thermistor/NTC sensor
repair or replace damaged wiring
clean corroded connectors
if the PCB input is damaged, replace the PCB
Refer to the Ravenheat service documentation for the detailed procedure. Only a qualified engineer should carry out these repairs.
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Affected Models
Ravenheat models that can display fault code E03:
| Model Family | Output Range | Frequency |
|---|---|---|
| All Ravenheat models | — | Possible |
Frequently Asked Questions
Replace the faulty thermistor/NTC sensor. According to the technical documentation, this is the first check on the list for E03.
E03 is not classified as a high-severity fault, so the boiler can be reset once. If E03 comes back, stop resetting: the underlying cause is still there and needs a qualified heating engineer.