Heatline Capriz 25/28 Fault codes & diagnostics

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

Combi Natural Gas 25-28 kW 2013-2018 Discontinued

Replaced by: Capriz2

Download the Heatline Capriz 25/28 manual The official installation & service manual (PDF) — the exact document these fault codes were verified against. PDF

This boiler uses LED flash patterns

Count the flashes in one repeating group before the pause. That number is your fault code. Do not reset until you have noted it. How to read fault codes →

Severity at a glance

Each cell = one fault code. Hover to identify.
10 High 1 Medium 1 Low
Just want the most common Heatline Capriz 25/28 faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 12 documented codes

Tap any card for details

LED / flash-pattern codes
Flashing 30

Your boiler has detected an issue with the sensor that monitors the temperature of the water circulating in your radiators.

High Engineer only £90-160

Parts commonly replaced

  • Central Heating (CH) NTC Temperature Sensor
  • Sensor wiring harness
Full explanation for Flashing 30
Flashing 40

Your boiler is struggling to work out the outside temperature because there is a problem with the external sensor or its wiring.

Low Engineer only £70-140

Parts commonly replaced

  • Outdoor temperature sensor
  • Control board connection lead

Related codes

Full explanation for Flashing 40
Flashing 50

Your boiler has identified a problem with how it moves air and exhaust gases through the system, causing it to shut down for safety.

High Engineer only £120-£240

Parts commonly replaced

  • Air Pressure Switch
  • Venturi Tube
  • Fan

Related codes

Full explanation for Flashing 50
Flashing 60

Your boiler has failed to light or maintain a flame, meaning you have no heating or hot water because the burner has shut down for safety.

High DIY-safe £100-£350

What to check first

  1. Check if other gas appliances, like a hob, are working to confirm your gas supply is active.
  2. If you have a prepaid gas meter, check that you have remaining credit.
  3. Press and hold the 'Reset' button for 2-5 seconds to see if the boiler restarts.

Parts commonly replaced

  • Ignition Electrode
  • Gas Valve
  • Printed Circuit Board (PCB)

Related codes

Full explanation for Flashing 60
Flashing 70

Your boiler's hot water sensor has detected a fault, meaning you may experience inconsistent water temperatures or no hot water at all.

Medium Engineer only £90-160

Parts commonly replaced

  • DHW Thermistor (NTC Sensor)
  • Wiring harness

Related codes

Full explanation for Flashing 70
Flashing 80

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

High DIY-safe £0-120

What to check first

  1. Locate the filling loop (usually a silver flexible hose) underneath the boiler.
  2. Slowly open the one or two taps/levers on the hose until you hear water flowing.
  3. Watch the pressure gauge and close the taps once the needle reaches between 1 and 1.5 bar.

Parts commonly replaced

  • Filling loop
  • Expansion vessel
  • Pressure relief valve
Full explanation for Flashing 80
Flashing 90

Your boiler has become too hot and has automatically shut down to prevent damage or safety issues.

High DIY-safe £90-250

What to check first

  1. Check that all radiator valves are fully open to allow water to circulate
  2. Ensure there is enough pressure in the system by checking the gauge
  3. Once the boiler has cooled down, press the reset button

Parts commonly replaced

  • Overheat Thermostat
  • Circulation Pump
  • Main Heat Exchanger Cleaning

Related codes

Full explanation for Flashing 90
Digital codes
F1

Your boiler has failed to ignite, meaning it cannot light the gas to provide heat or hot water for your home.

High DIY-safe £120-350

What to check first

  1. Check that your gas pre-payment meter (if you have one) has credit.
  2. Ensure your gas stop tap is fully open and other gas appliances are working.
  3. Press and hold the 'Reset' button (the one with the flame/cross symbol) for five seconds.

Parts commonly replaced

  • Ignition Electrode
  • Gas Valve
  • Printed Circuit Board (PCB)

Related codes

Full explanation for F1
F2

Your boiler's internal thermometer has stopped working correctly, meaning the system can no longer monitor the temperature of the water used for your heating.

High Engineer only £90-160

Parts commonly replaced

  • Central Heating (CH) NTC sensor
  • Wiring harness connectors

Related codes

Full explanation for F2
Lock-out

Your boiler has shut down to protect itself, likely because it got too hot or failed to light the gas flame.

High DIY-safe £90-180

What to check first

  1. Turn the main control knob to the 'Off' position.
  2. Wait for at least 15 seconds for the system to reset.
  3. Turn the control knob back to the 'On' or 'Winter' position and check if the flame ignites.

Parts commonly replaced

  • Overheat Thermostat
  • Ignition Electrode
  • Gas Valve

Related codes

Full explanation for Lock-out
Low water pressure

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

High DIY-safe £0-120

What to check first

  1. Locate the filling loop (a flexible silver hose) underneath the boiler.
  2. Slowly open the one or two taps/levers on the filling loop until you hear water entering.
  3. Watch the pressure gauge until it reaches between 1.0 and 1.5 bar, then close the taps tightly.

Parts commonly replaced

  • Filling loop
  • Expansion vessel
  • Pressure sensor
Full explanation for Low water pressure
Overheat

Your boiler has switched itself off because the water inside it has become too hot, usually due to a lack of circulation or a blockage.

High DIY-safe £100-£350

What to check first

  1. Check that your radiator valves are fully open to allow water to flow.
  2. Check the boiler pressure gauge and top up to 1.5 bar if it is too low.
  3. Reset the boiler using the control knob to see if the fault clears.

Parts commonly replaced

  • Circulation pump
  • Overheat thermostat
  • Heat exchanger

Related codes

Full explanation for Overheat
Status & diagnostic codes

7 operating states & engineer diagnostics

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

30 Status Your boiler has stopped heating your radiators because it is unable to accurately measure the internal temperature of the water being sent to them. 40 Status Your boiler is struggling to accurately read the outside temperature, which may cause your heating to run inefficiently or not turn on correctly. 50 Status Your boiler is failing to confirm that the internal fan is effectively clearing waste gases, so it has safely shut itself down to prevent unsafe operation. 60 Status Your boiler is failing to light the burner, meaning it cannot produce heat or hot water because it is not sensing a flame or receiving gas properly. 70 Status Your boiler is having trouble detecting the temperature of the water used for your taps and shower, so it has stopped heating your hot water to prevent it from getting too hot. 80 Status Your boiler has detected that the water temperature has risen beyond the safe limit and has shut itself down to prevent damage. 90 Status Your boiler has detected that the water inside the system is getting too hot, so it has safely shut itself down to prevent damage.