Boiler shows D1, often related to low system pressure or circulation issues, heating may not start.
Safety Warning
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
How to Fix / Troubleshooting
Safety first: Allow the system to cool before topping up pressure to avoid scalding from hot water.
Homeowner checks:
- Check the pressure gauge; if below 1.0 bar, top up using the filling loop until 1.2–1.5 bar when cold.
- Bleed radiators to remove air, then re-check and adjust pressure.
- Inspect visible pipework and radiators for leaks.
Engineer checks:
- Test the Worcester pressure sensor for correct output and replace if faulty.
- Check expansion vessel charge pressure and recharge or replace if waterlogged.
- Investigate and repair any hidden leaks in the system.
If pressure drops repeatedly, a leak or expansion issue must be resolved rather than continually topping up.
Repair Difficulty
Required Part
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