Worcester Bosch Intermittent Overheat / Flow Restriction

Boiler frequently needs resetting, with no consistent error code, especially during hot water use.

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

Partially blocked plate or primary heat exchanger, Pump intermittently failing, Air in system, Faulty NTC sensors intermittently open-circuit

Safety first: Repeated lockouts indicate a fault that must be investigated; do not keep resetting indefinitely.

User checks:

Engineer actions:

Check pump operation under both CH and DHW modes; replace if intermittent.
Inspect and clean the plate and primary heat exchangers as needed.
Test all NTC sensors for intermittent faults by wiggling wiring while monitoring resistance.
Flush the system and fit a filter to reduce debris-related restrictions.

Hard 4/5

Primary Circulating Pump

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