Chaffoteaux Calydra 23 Green Fault codes & diagnostics

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

Combi Natural Gas 23 kW 2000-2005 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 23 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 missing its basic supply of gas, water, or electricity.

High DIY-safe £100-280

What to check first

  1. Check if your gas supply is turned on and other gas appliances are working.
  2. Ensure the boiler is plugged in and the fused spur switch is in the 'on' position.
  3. Check your property's consumer unit (fuse box) to see if a circuit breaker has tripped.
  4. Verify that the water pressure gauge is between 1 and 1.5 bar; top up if necessary.

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 run again.

High DIY-safe £100-280

What to check first

  1. Turn off the boiler and allow it to cool for 20 minutes.
  2. Ensure all radiator valves are fully open to allow water to circulate.
  3. Press the Reset button on the front control panel to restart the system.

Parts commonly replaced

  • Overheat Thermostat
  • Circulation Pump
  • Temperature Sensor (NTC)

Related codes

Full explanation for 01
01 to 99

Your boiler is displaying a log of the most recent error that occurred, which may or may not still be an active issue.

Low DIY-safe £0-120

What to check first

  1. Check if the boiler is currently providing heating and hot water.
  2. Try resetting the boiler by turning the selector switch to 'Reset' for a few seconds.
  3. Monitor the display to see if a specific live fault code replaces this message.

Parts commonly replaced

  • None (information only)
  • PCB (if display is frozen)

Related codes

Full explanation for 01 to 99
03

Your boiler is failing to light the gas burner, which means it cannot provide heat or hot water.

High DIY-safe £100-£280

What to check first

  1. Check if other gas appliances in your home, like a hob, are working to confirm your gas supply is on.
  2. Ensure your gas meter has credit if you use a prepay meter.
  3. Press the 'Reset' button on the front control panel and wait for the boiler to restart.

Parts commonly replaced

  • Ignition Electrode
  • Flame Sensing Probe
  • Gas Valve

Related codes

Full explanation for 03
05

Your boiler has detected very cold temperatures and is circulating water to prevent the internal pipes from freezing.

Low DIY-safe

What to check first

  1. Ensure the boiler remains switched on at the mains power
  2. Check that your room thermostat is turned up
  3. Ensure any exposed pipes in unheated areas like garages are adequately insulated

Related codes

Full explanation for 05
06

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

Low DIY-safe

What to check first

  1. Ensure the boiler remains plugged in and switched on at the wall
  2. Check that your main gas supply is active
  3. Wait for the boiler to complete its cycle and the temperature to rise

Related codes

Full explanation for 06
07

Your boiler has stopped working because water is not moving around the internal system properly, causing it to shut down to prevent overheating.

High DIY-safe £150-£350

What to check first

  1. Check that the boiler pressure gauge is between 1 and 1.5 bar
  2. Ensure all radiator valves and isolation valves under the boiler are fully open
  3. Gently bleed your radiators to remove any trapped air pockets
  4. Reset the boiler using the 'R' or Reset button

Parts commonly replaced

  • Circulation Pump
  • Primary Heat Exchanger
  • Main PCB

Related codes

Full explanation for 07
08

Your boiler has detected that there is not enough water pressure in the system to operate safely.

High DIY-safe £0-120

What to check first

  1. Locate the filling loop (usually a silver braided hose with small valves underneath the boiler).
  2. Open the valves slowly until you hear water flowing and the pressure gauge reaches between 1.0 and 1.5 bar.
  3. Close the valves tightly and restart the boiler.

Parts commonly replaced

  • Filling loop
  • Expansion vessel
  • Pressure sensor

Related codes

Full explanation for 08
09

Your boiler's hot water sensor has failed, meaning it cannot accurately measure the temperature of the water going to your taps.

Medium Engineer only £90-160

Parts commonly replaced

  • DHW Thermistor (NTC sensor)
  • Wiring harness connectors

Related codes

Full explanation for 09
10

Your boiler's hot water sensor has failed, meaning it cannot accurately measure or deliver hot water to your taps.

Medium Engineer only £90-160

Parts commonly replaced

  • DHW NTC Thermistor
  • Thermistor O-ring seal

Related codes

Full explanation for 10
Showing 11–20 of 21
12

Your boiler's internal thermometer for the heating system has stopped working, meaning the unit cannot safely tell how hot the water is and has shut down as a precaution.

High Engineer only £90-160

Parts commonly replaced

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

Your boiler has failed to stay lit and is repeatedly trying to restart the burner to restore heating and hot water.

High Engineer only £120-280

Parts commonly replaced

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

Related codes

Full explanation for 18
20

Your boiler has stopped working because of an internal electrical connection issue between its main control components.

High Engineer only £120-£350

Parts commonly replaced

  • Main PCB
  • Wiring Loom
Full explanation for 20
23

Your boiler has stopped working because the internal fan is spinning too slowly to safely clear exhaust gases.

High Engineer only £180-350

Parts commonly replaced

  • Fan unit
  • Main circuit board (PCB)
  • Air pressure switch
Full explanation for 23
24

Your boiler has detected a problem with the fan that safely removes exhaust gases, meaning the system has shut down to prevent safety issues.

High Engineer only £180-350

Parts commonly replaced

  • Fan Assembly
  • Main Control Board (PCB)
  • Wiring Harness

Related codes

Full explanation for 24
25

Your boiler has lost communication with the sensor that monitors the hot water temperature in your storage cylinder, meaning it cannot safely heat your water.

High Engineer only £120-£190

Parts commonly replaced

  • Hot water storage cylinder thermistor (NTC sensor)
  • Sensor wiring harness

Related codes

Full explanation for 25
26

Your boiler has detected a problem with the temperature sensor for the hot water storage cylinder, meaning it cannot accurately monitor the water temperature.

Medium Engineer only £90-160

Parts commonly replaced

  • Domestic Hot Water (DHW) Thermistor
  • Wiring harness
  • NTC Sensor

Related codes

Full explanation for 26
29

Your boiler is stuck in heating mode, which means your radiators might stay hot even when you only want hot water, or you may find you have no hot water at all.

High Engineer only £180-320

Parts commonly replaced

  • Three-way valve motor
  • Complete Diverter Valve assembly
  • Valve cartridge
Full explanation for 29
31

Your boiler's main control system is having trouble talking to the front display panel, meaning the boiler cannot receive the instructions it needs to provide heating and hot water.

High Engineer only £140-£280

Parts commonly replaced

  • Display PCB
  • Main Control PCB
  • Wiring Loom

Related codes

Full explanation for 31
32

Your boiler's computer brains aren't talking to each other properly, causing 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 is making unusual sounds because the water pressure is too low or there are air bubbles trapped inside the system.

Medium DIY-safe £0-120

What to check first

  1. Check the pressure gauge and use the filling loop to top it up to 1.5 bar
  2. 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