Worcester Bosch Return Temperature Sensor (NTC) Fault

Boiler displays E3, may run briefly then stop, often associated with return temperature sensing.

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

Possible Causes

Failed return NTC sensor, Damaged NTC harness, Faulty PCB sensor circuit

Safety first: Turn off power at the fused spur before accessing internal components.

Engineer actions:

Locate the return NTC sensor on the return pipe entering the boiler.
Measure resistance and compare with manufacturer’s NTC chart.
Inspect wiring for chafing or water ingress from leaks; repair or replace harness as needed.
Replace the return NTC if readings are out of range or intermittent.
If fault persists, test and if necessary replace the control PCB.

Medium 3/5

Return Temperature Sensor (NTC)

Check Price on Amazon

We may earn a commission from links on this page.