Chaffoteaux Calydra 24 Green Fault codes & diagnostics

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

Combi Natural Gas 24 kW 2001-2006 Discontinued

Replaced by: Chaffoteaux Britony

This boiler uses indicator light combinations

Note which lights are on, off, or flashing and at what speed. Match the combination to the cards below. Do not reset until you have noted the pattern. How to read fault codes →

Severity at a glance

Each cell = one fault code. Hover to identify.
14 High 4 Medium 3 Low
Just want the most common Chaffoteaux Calydra 24 Green faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 21 documented codes

Tap any card for details

LED / flash-pattern codes
Red indicator lit

Your boiler has shut down because it is lacking one of its essential supplies like gas, water, or power.

High DIY-safe £100-£350

What to check first

  1. Check if other gas appliances in your home, like a hob, are working.
  2. Ensure the boiler's power switch is on and no fuses have tripped in your consumer unit.
  3. Check the pressure gauge and top it up to 1.5 bar if it is below 1.0 bar.
  4. Press the 'Reset' button on the front control panel.

Parts commonly replaced

  • Gas Valve
  • Ignition Electrode
  • Printed Circuit Board (PCB)
Full explanation for Red indicator lit
Digital codes
01

Your boiler has switched itself off because it has reached an unsafe temperature and needs to cool down before it can be used again.

High DIY-safe £120-350

What to check first

  1. Wait 20 minutes for the boiler to cool down.
  2. Check that your radiator valves are open and not turned to zero.
  3. Press the 'Reset' button on the front control panel.
  4. Check the system pressure gauge is between 1.0 and 1.5 bar.

Parts commonly replaced

  • Overheat Thermostat
  • Circulation Pump
  • Main Heat Exchanger (Cleaning or Replacement)

Related codes

Full explanation for 01
01 to 99

Your boiler is displaying a list of the most recent historical errors stored in its memory rather than an active, ongoing fault.

Low DIY-safe £0-80

What to check first

  1. Press the Reset button once to clear the menu
  2. Monitor the boiler to see if a specific active fault code appears
  3. Ensure your system pressure is topped up to roughly 1.5 bar

Parts commonly replaced

  • None (Software Menu)
Full explanation for 01 to 99
03

Your boiler is failing to light the gas or isn't recognizing that a flame is present, meaning your heating and hot water will not work.

High DIY-safe £120-£350

What to check first

  1. Check if other gas appliances in your home are working to ensure gas is being supplied
  2. Check if your gas meter has credit (if using a pre-payment meter)
  3. Press the Reset button once to see if the boiler restarts

Parts commonly replaced

  • Ignition electrode
  • Flame sensing probe
  • Gas valve
  • PCB

Related codes

Full explanation for 03
05

Your boiler has detected that the internal water temperature is very low and has automatically turned on the pump to prevent the pipes from freezing.

Low DIY-safe £0-80

What to check first

  1. Ensure the boiler power supply remains switched on
  2. Check that the gas supply is active
  3. Increase the room thermostat temperature slightly to encourage the boiler to fire up
  4. Check that any external condensate pipes are not frozen or blocked

Parts commonly replaced

  • None (Normal operation)
  • NTC Temperature Sensor

Related codes

Full explanation for 05
06

Your boiler has detected very low temperatures and is automatically running the pump and burner to prevent the internal pipes from freezing.

Low DIY-safe

What to check first

  1. Ensure the boiler remains connected to the power supply
  2. Check that the gas supply is turned on
  3. Increase the room thermostat temperature slightly to help warm the system
  4. Check that any external pipes are properly insulated

Related codes

Full explanation for 06
07

Your boiler has stopped working because water is not moving around the internal pipes as it should.

High DIY-safe £150-350

What to check first

  1. Check that your radiators are turned clockwise to the open position
  2. Ensure the boiler pressure gauge is between 1 and 1.5 bar
  3. Check if any external valves on the pipework have been accidentally closed
  4. Press the reset button to see if the system clears the air block

Parts commonly replaced

  • Circulation Pump
  • Flow Switch
  • Main Heat Exchanger

Related codes

Full explanation for 07
08

Your boiler has lost water pressure and cannot operate safely without being topped up.

High DIY-safe £0-120

What to check first

  1. Locate the filling loop valves underneath the boiler
  2. Slowly open both valves to allow water into the system
  3. Close the valves once the pressure gauge reaches 1.5 bar

Parts commonly replaced

  • Filling loop
  • Expansion vessel
  • Pressure relief valve

Related codes

Full explanation for 08
09

Your boiler's hot water sensor has failed, which means the system cannot accurately measure the water temperature for your taps.

Medium Engineer only £90-160

Parts commonly replaced

  • DHW NTC Thermistor
  • Sensor wiring harness

Related codes

Full explanation for 09
10

Your boiler's hot water sensor has failed, meaning it can no longer accurately measure and control the temperature of the water coming out of your taps.

Medium Engineer only £90-160

Parts commonly replaced

  • Domestic Hot Water (DHW) Thermistor
  • NTC Sensor

Related codes

Full explanation for 10
Showing 11–20 of 21
12

Your boiler has stopped providing heating because a internal sensor monitoring the temperature is no longer working correctly.

High Engineer only £90-160

Parts commonly replaced

  • Central Heating (CH) NTC Thermistor
  • Connecting wiring harness
Full explanation for 12
18

Your boiler has failed to light several times and is trying again, which usually means it is struggling to detect a flame or there is a problem with the gas supply.

High DIY-safe £100-280

What to check first

  1. Check that your gas emergency control valve is in the 'on' position
  2. If you have a prepay meter, check that you have sufficient credit
  3. Check if other gas appliances, like a hob, are working correctly
  4. Press the Reset button to see if the boiler clears the fault

Parts commonly replaced

  • Ignition Electrode
  • Flame Sensing Probe
  • Gas Valve

Related codes

Full explanation for 18
20

Your boiler has detected an internal electrical communication error, meaning the main control board cannot talk to the sensors or parts correctly.

High Engineer only £120-£350

Parts commonly replaced

  • Wiring Harness
  • Main PCB (Printed Circuit Board)
  • Thermistors
Full explanation for 20
23

Your boiler has stopped working because the fan that removes waste gases is spinning too slowly to operate safely.

High Engineer only £180-350

Parts commonly replaced

  • Fan assembly
  • Printed Circuit Board (PCB)
  • Venturi tube

Related codes

Full explanation for 23
24

Your boiler has detected a problem with the fan that safely removes exhaust fumes, which means the system has shut down as a safety precaution.

High Engineer only £180-£350

Parts commonly replaced

  • Fan assembly
  • Printed Circuit Board (PCB)
  • Wiring harness
Full explanation for 24
25

Your boiler has lost its connection to the sensor that monitors the temperature of the internal hot water storage tank.

High Engineer only £90-160

Parts commonly replaced

  • Domestic Hot Water (DHW) Cylinder NTC Sensor
  • Wiring Harness

Related codes

Full explanation for 25
26

Your boiler has lost communication with the temperature sensor inside the hot water cylinder, meaning it can no longer monitor how hot your water is.

High Engineer only £100-190

Parts commonly replaced

  • NTC Cylinder Temperature Sensor
  • Wiring Harness
  • Main Control PCB

Related codes

Full explanation for 26
29

Your boiler is currently stuck in central heating mode, which means you might not get hot water at your taps when you need it.

Medium Engineer only £160-280

Parts commonly replaced

  • Three-way valve motor
  • Three-way valve cartridge
Full explanation for 29
31

Your boiler's main control panel is having trouble talking to the internal display, meaning the system cannot receive or process your commands correctly.

High Engineer only £140-280

Parts commonly replaced

  • Display PCB
  • Main Circuit Board (PCB)
  • Ribbon Cable Harness

Related codes

Full explanation for 31
32

Your boiler's internal computer is having trouble talking to its main control board, which has caused the system to stop working for safety.

High Engineer only £250-450

Parts commonly replaced

  • Main PCB
  • Wiring Loom

Related codes

Full explanation for 32
Showing 21–21 of 21
Noises in CH system

Your boiler or radiators are making unusual sounds because there is trapped air in the system or the water pressure has dropped too low.

Medium DIY-safe £0-120

What to check first

  1. Check the pressure gauge on the front of the boiler and top it up to 1.5 bar using the filling loop if it is too low.
  2. Carefully bleed your radiators using a radiator key to release any trapped air.
  3. Restart the boiler to see if the noises persist.

Parts commonly replaced

  • Automatic air vent
  • Expansion vessel
  • Filling loop valve
Full explanation for Noises in CH system