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Seeing the Worcester E5 error on your boiler display? This is a Worcester Bosch boiler error that indicates a fault with the flow temperature sensor-a key component responsible for monitoring the temperature of the water circulating through your heating system. The E5 code is one of several boiler error codes that can appear on a Worcester Bosch boiler, and understanding these boiler error codes is important for accurate troubleshooting. At 0800 Homefix, we help homeowners fix this common issue quickly and safely. In this guide, we explain what the E5 code means, what causes it, and how to restore your Worcester boiler to full function.
What Is the Worcester E5 Error Code?
The Worcester E5 fault refers to a failure of the flow temperature sensor, sometimes also caused by an issue with the sensor’s electrical circuit. The boiler monitors water temperature to regulate burner operation, ensure efficiency, and prevent overheating. If it can’t get a reliable reading, the system will shut down for safety. An incorrect installation position of the sensor can also trigger this fault. Additionally, the E5 code may indicate that the temperature sensor is defective.
You may see:
E5 on Worcester boiler
Worcester boiler showing E5
E5 sensor error Worcester
temperature sensor defective
temperature sensor is defective
This is usually a blocking fault, which means your boiler won’t function again until the issue is resolved.
What Does the Flow Temperature Sensor Do?
This sensor plays a critical role in your boiler’s internal monitoring system. It helps the boiler maintain the correct temperature in the central heating (CH) flow circuit. A defective or disconnected sensor can lead to issues like:
Uncontrolled water temperature
Boiler overheating
Inaccurate modulation of the burner
Some models may use a Negative Thermistor Coefficient (NTC) sensor, which decreases resistance as temperature increases. If damaged, the readings become unreliable. Some faults may be related to a flow negative thermistor coefficient, which indicates a defective NTC sensor in the CH flow. Additionally, some Worcester Bosch boilers use a differential sensor to monitor temperature differences, and issues with this sensor can also cause faults. It is important to install the flow temperature sensor correctly to avoid error codes and ensure proper boiler operation.
Common Causes of E5 on Worcester Bosch Boilers
The Worcester flow temperature fault may result from:
Sensor degradation due to age or limescale buildup
Loose electrical connector contacts
Short circuit, sensor short circuit, or open circuit in the sensor wiring
Pressure sensor connection issues
Pressure sensor defective
Incorrect sensor installation position
Water ingress into the sensor or control board
A defective burner control unit misinterpreting data
As part of troubleshooting, check pressure sensor connection to ensure it is secure and properly installed.
Some boilers may also throw this error due to:
Sensor cable damage
Faulty control unit firmware
Internal overheating without proper sensor feedback
Symptoms to Watch Out For
Before or alongside the E5 sensor error Worcester, you might notice:
Boiler frequently locking out
Inconsistent heating performance
Radiators only partially warming
Unusual boiler noises or overheating
Display flashing between error codes and temperature values
Display showing a temperature difference or temperature difference greater than expected between flow and return sensors
Flow sensor short circuit error appearing on the display
How to Troubleshoot a Worcester E5 Fault
If you’re comfortable checking basic elements:
Reset the Boiler: Temporary glitches can sometimes be cleared.
Check Display Readings: Sudden temperature spikes or blank readings can suggest a sensor issue.
Check Pressure Sensor and Connection: Inspect the pressure sensor and its connection for faults. If the sensor is faulty, consider pressure sensor replace to resolve pressure-related issues.
Inspect Wiring (Visually Only): Look for loose wires or moisture at the sensor port.
Inspect Bus Communication Cable: Check the bus communication cable for any faults or disconnections, as this can cause communication errors within the boiler system.
Verify Service Mode Switch Position: Ensure the service mode switch is set to the correct position (minimum or maximum) as incorrect settings can impact boiler operation and error codes.
Confirm Pressure: Low pressure may not directly cause E5 but could stress other components.
⚠️ If the issue persists, or if you suspect sensor failure, call a Gas Safe engineer immediately. Do not attempt electrical tests yourself.
Fixing the Worcester Flow Temperature Sensor Fault
At 0800 Homefix, we offer quick diagnosis and affordable repair solutions:
Flow temperature sensor testing and replacement
Electrical checks and cable replacements
Resetting control systems and clearing memory faults
Checking or replacing the heat control module (HCM)
Inspecting the gas valve relay and modulating gas valve for faults
Checking the gas valve for operation and possible gas valve leak
Inspecting or adjusting the gas ratio control valve and air gas ratio control
Checking the ignition burner control unit and programmer interface module for faults
Full boiler safety checks post-repair
We work with all Worcester Bosch models, including:
Greenstar Si Compact
CDI Classic Combi Boiler
CDI Classic Regular
Cost to Fix a Worcester E5 Fault
Here’s what you can expect:
Sensor replacement: £90–£150
Pressure sensor replace: £90–£150
Wiring or connection repair: £80–£130
Full diagnostic and reset: £60–£90
Vent system repair (if related to pressure or sensor faults): £100–£250
We offer transparent, no-surprise pricing with genuine replacement parts.
How to Prevent E5 Errors in the Future
Annual boiler servicing should include checking the outside temperature sensor, hot water sensor, hot water temperature sensor, flow and safety sensor, ch flow NTC sensor, heat exchanger, and heat exchanger temperature sensor. Inspect the heating block for sensor issues, and monitor the primary flow temperature for any abnormal flow temperature rise or flow temperature rising.
Inspect the integrity flue system, flue gas venting, and flue gas thermostat for blockages or faults. Also, check the interconnected room air supply to ensure proper ventilation.
Verify minimum burner load settings, and test the high limit thermostat and safety temperature limiter to ensure all safety devices are functioning correctly.
Maintain the central heating system regularly. These preventive steps apply to both system boiler and combi boilers.
Keep system pressure in the recommended range
Install a magnetic filter to reduce sludge buildup
Avoid topping up the boiler too frequently (this adds fresh limescale-rich water)
Keep boiler ventilation clear and ambient conditions stable
Avoid electrical power interruption, and if a fault occurs repeatedly, seek professional help to prevent ongoing issues.
Helpful Resources
Worcester Bosch Support: https://www.worcester-bosch.co.uk
Gas Safe Register: https://www.gassaferegister.co.uk
UK Boiler Safety Advice: https://www.gov.uk
Frequently Asked Questions
What does the E5 error mean on my Worcester boiler?
It means the flow temperature sensor is faulty or disconnected, and the boiler can’t safely monitor heat levels.
Can I fix the Worcester E5 fault myself?
No. Only a qualified engineer should handle sensor diagnostics and electrical testing.
Is it dangerous to keep resetting the boiler after an E5 fault?
Yes. This bypasses important safety checks and could lead to overheating.
Why does my Worcester boiler keep showing E5?
This can result from a failing sensor, damaged wires, faulty PCB signals, or issues with the code plug. Problems such as an incorrect code plug, incompatible code plug, or incorrect code plug detected can cause persistent errors-checking for the correct code plug is important. Additionally, faults with the fuel supply, gas supply, or gas line can contribute to this issue.
Can 0800 Homefix fix this same day?
Yes-we offer same-day visits and carry replacement sensors for most Worcester Bosch models.