Zanussi Ultra Combi Fault codes & diagnostics

3 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.

Combi Natural Gas 2005-2017 Discontinued
GC Numbers 47-002-0147-002-02
Download the Zanussi Ultra Combi manual The official installation & service manual (PDF) — the exact document these fault codes were verified against. PDF

The fault code is already on your display

Note it down before pressing reset — resetting clears the code immediately. How to read fault codes →

Just want the most common Zanussi Ultra Combi faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 3 documented codes

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C0

Your boiler has detected a minor internal communication error and needs to be restarted to clear the fault and resume normal operation.

Low DIY-safe

What to check first

  1. Locate the reset button or dial on the front control panel
  2. Press and hold the reset button for 3 to 5 seconds
  3. Wait 2 minutes for the system to cycle and check if the error code clears

Parts commonly replaced

  • Printed Circuit Board (PCB)

Related codes

Full explanation for C0
C2

Your boiler has lost communication with its internal computer chip, meaning the main control board no longer recognizes the specific model it is supposed to be operating.

High Engineer only £100-£350

Parts commonly replaced

  • Boiler Chip Card (BCC)
  • Printed Circuit Board (PCB)

Related codes

Full explanation for C2
L1

Your boiler has shut down because the water inside it has become too hot, usually due to a lack of circulation or a blockage in the system.

High DIY-safe £100-350

What to check first

  1. Check that your radiator valves are fully open.
  2. Ensure the boiler pressure is between 1 and 1.5 bar on the gauge.
  3. Reset the boiler by turning the control knob to 'Reset' and then back to 'On'.

Parts commonly replaced

  • Pump
  • Flow Thermistor
  • Heat Exchanger

Related codes

Full explanation for L1
Status & diagnostic codes

4 operating states & engineer diagnostics

Not faults — these are normal operating states. Tap to expand.

oF Diagnostic Your boiler is in a standby or programming mode and thinks it has been told to stay switched off. P1 Diagnostic Your boiler is displaying a service setting notification rather than a breakdown, indicating the internal pump is being told to run at its maximum speed. SE Diagnostic Your boiler is simply reminding you that its annual service is due soon; it is a notification rather than a breakdown. uP Diagnostic Your boiler is currently stuck in its startup or programming sequence and is not yet ready to provide heat or hot water.