Worcester D5 fault: NTC sensor readings out of range
NTC sensors tell the boiler how hot the water is. When a reading drifts outside plausible limits, the appliance stops rather than working blind.
A D5 sensor fault explained in plain terms
Sensors are tested by resistance against the manufacturer's temperature table, which is quick and definitive. Corroded plugs, chafed harnesses and sensors coated in sludge all shift readings. Where a sensor tests fine, we look at whether real system temperatures are genuinely spiking because of poor circulation, since that produces the same code from healthy hardware.
A D5 sensor fault — the facts that change the job
- Resistance testing beats guesswork on sensor faults
- Sludge coating changes the sensor's response time
- Intermittent codes often trace to connectors, not the sensor
- System water quality affects sensor life directly
- A magnetic filter protects sensors as well as the pump
Where we deal with this
Scope of work
- Domestic boiler installation
- Boiler servicing
- Boiler maintenance and repair
Book a visit for a D5 sensor fault
The honest position: Test, do not guess. A resistance check separates a failing sensor from a system running too hot.
Jamie Crawford Heating is based at 24 Bristol Road, Radstock, BA3 3EE.
Related help pages
- Fault differentiationIdeal L2: why the same code means different repairs
- Legacy display codeWorcester 1016: how a numeric-only display shows a fault
- Standing pilot faultPilot light will not stay lit: the thermocouple and draught checks
- Symptom guideNo hot water but the heating works: what that combination means
- Noise diagnosisNoisy pipework and kettling: telling the two apart by sound
- Repair or replaceWhen a boiler repair genuinely stops making sense
Services that cover this
Questions we get asked
- Why did the fault clear itself?
- Intermittent connections behave like that. It will return, usually more often, until the joint or sensor is replaced.
- Are sensors expensive?
- They are among the cheaper boiler parts, which is why proper testing matters more than the part cost.
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