Baxi Duo-tec Combi HE A Fault codes & diagnostics

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

Combi Natural Gas 24-40 kW 2008-2015 Discontinued

Replaced by: Baxi Platinum+

The Duo-tec range comes in 4 types

Pick the one you have. The fault codes, GC numbers and manual differ by type.

Each model has its own manual A family spans several manuals, one per model or generation. Pick your model above and its page has the manual its fault codes were read from.

The fault code is already on your display

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

Severity at a glance

Each cell = one fault code. Hover to identify.
1 Emergency 18 High

All 19 documented codes

Tap any card for details

20

Your boiler has detected an issue with the sensors that monitor the internal temperature, causing it to stop operating to keep your system safe.

High Engineer only £150-250 Shared across the Duo-tec Combi range

Parts commonly replaced

  • NTC Temperature Sensor
  • Wiring harness
  • PCB

Related codes

28

Your boiler is struggling to send water through your radiators or taps because it has detected an issue with the sensor that measures the water temperature as it leaves the unit.

High Engineer only £150-250 Shared across the Duo-tec Combi range

Parts commonly replaced

  • NTC sensor
  • Wiring harness

Related codes

50

Your boiler has detected a problem with the temperature sensors, meaning it cannot accurately measure how hot the water is and has stopped working to keep you safe.

High Engineer only £150-250 Shared across the Duo-tec Combi range

Parts commonly replaced

  • NTC Temperature Sensor
  • Wiring Harness

Related codes

110

Your boiler has stopped working because it has detected that the water inside it has become dangerously overheated.

High Engineer only £120-250 Shared across the Duo-tec Combi range

Parts commonly replaced

  • NTC temperature sensor
  • Primary heat exchanger
  • Pump

Related codes

119

Your boiler has detected that the water pressure inside the system has dropped too low to operate safely.

High DIY-safe £0-£120 Shared across the Duo-tec Combi range

What to check first

  1. Locate the external filling loop, which is usually a small silver braided hose with one or two valves located underneath the boiler.
  2. Open the valve(s) slowly to allow mains water into the system until the pressure gauge on the front of the boiler reads between 1.0 and 1.5 bar.
  3. Close the valve(s) tightly and check that the error code clears.

Parts commonly replaced

  • Filling loop
  • Pressure relief valve
  • Pressure sensor

Related codes

125

Your boiler has detected that the water is not circulating properly through the system, often because the water has heated up too quickly or isn't moving away from the internal heat exchanger.

High Engineer only £150-300 Shared across the Duo-tec Combi range

Parts commonly replaced

  • Central heating pump
  • System filter
  • Diverter valve

Related codes

130

Your boiler has detected that the temperature of the exhaust gases leaving the flue is too high, causing it to shut down for safety reasons.

High Engineer only £150-300 Shared across the Duo-tec Combi range

Parts commonly replaced

  • Flue gas thermostat
  • Primary heat exchanger
  • NTC sensor

Related codes

133

Your boiler has failed to ignite the flame needed to heat your water and has safely shut itself down as a precaution.

High Engineer only £120-250 Shared across the Duo-tec Combi range

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Printed Circuit Board (PCB)

Related codes

160

Your boiler has detected a problem with the internal fan that pushes exhaust gases out, meaning it has safely shut itself down to prevent unsafe operation.

High Engineer only £150-300 Shared across the Duo-tec Combi range

Parts commonly replaced

  • Fan assembly
  • Wiring harness
  • Printed Circuit Board (PCB)

Related codes

E20

Your boiler has lost the ability to monitor the temperature of the water circulating through your radiators, so it has shut down to prevent overheating.

High Engineer only £120-200 Shared across the Duo-tec Combi range

Parts commonly replaced

  • Central Heating NTC Sensor
  • Wiring harness

Related codes

E28

Your boiler has detected a faulty sensor that monitors the temperature of the gases leaving your flue, which has caused the boiler to stop working to keep you safe.

High Engineer only £150-250 Shared across the Duo-tec Combi range

Parts commonly replaced

  • Flue NTC Sensor
  • Wiring Harness

Related codes

E50

Your boiler is currently unable to sense the temperature of your hot water, which means it has stopped providing hot water to your taps and shower.

High Engineer only £120-220 Shared across the Duo-tec Combi range

Parts commonly replaced

  • Domestic Hot Water (DHW) NTC Sensor

Related codes

E110

Your boiler has detected that it has become dangerously overheated and has automatically shut itself down to prevent damage.

High Engineer only £120-250 Shared across the Duo-tec Combi range

Parts commonly replaced

  • Pump
  • Diverter Valve
  • Heat Exchanger
  • NTC Sensor

Related codes

E119

Your boiler has stopped working because the water pressure inside the system has dropped too low to operate safely.

High DIY-safe £80-150 Shared across the Duo-tec Combi range

What to check first

  1. Locate the external filling loop, which is usually a flexible silver braided hose connecting two pipes under the boiler.
  2. Open the small valve or tap on the filling loop to allow cold mains water to enter the system.
  3. Watch the pressure gauge on the front of the boiler and close the valve once the needle reaches between 1.0 and 1.5 bar.

Parts commonly replaced

  • Pressure Relief Valve
  • Pressure Gauge
  • Expansion Vessel

Related codes

E125

Your boiler has detected that the water inside the system is not flowing properly, which prevents it from heating your home or providing hot water safely.

High Engineer only £150-350 Shared across the Duo-tec Combi range

Parts commonly replaced

  • Central Heating Pump
  • Diverter Valve
  • System Filter

Related codes

E130

Your boiler has detected that the flue gases are getting too hot, so it has shut itself down as a safety precaution to prevent overheating.

Emergency Engineer only £150-300 Shared across the Duo-tec Combi range

Parts commonly replaced

  • Flue NTC sensor
  • Heat exchanger
  • Flue assembly

Related codes

E133

Your boiler is failing to light because it cannot detect a flame, which is often caused by a simple issue like the gas supply being switched off.

High Engineer only £120-250 Shared across the Duo-tec Combi range

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • PCB

Related codes

E160

Your boiler is struggling to clear exhaust gases safely because the internal fan that pushes air out is not responding correctly.

High Engineer only £200-350 Shared across the Duo-tec Combi range

Parts commonly replaced

  • Fan assembly
  • Wiring harness
  • Printed Circuit Board (PCB)

Related codes

E193

Your boiler is failing to confirm that water is flowing correctly through the system before it attempts to light the burner.

High Engineer only £150-300 Shared across the Duo-tec Combi range

Parts commonly replaced

  • Circulation pump
  • Flow sensor
  • Printed Circuit Board (PCB)

Related codes