Ravenheat 120 Fault codes & diagnostics

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

Combi Natural Gas 35 kW Discontinued

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46 High 3 Medium
Just want the most common Ravenheat 120 faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 49 documented codes

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01

Your boiler has failed to light and has shut itself down for safety, meaning you currently have no heating or hot water.

High DIY-safe £140-£380

What to check first

  1. Check that your gas pre-pay meter has credit (if applicable)
  2. Check that other gas appliances, like a hob, are working to ensure gas supply
  3. Press the reset button on the boiler control panel for 5 seconds

Parts commonly replaced

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

Related codes

Full explanation for 01
02

Your boiler has stopped running because it has detected an unusual temperature reading and needs to be restarted.

High DIY-safe £100-220

What to check first

  1. Locate the reset button or selector switch on the front control panel.
  2. Turn the switch to the 'R' (Reset) position for a few seconds and then back to 'On'.
  3. Wait for the boiler to complete its startup sequence to see if the heating or hot water returns.

Parts commonly replaced

  • Temperature Sensor (NTC thermistor)
  • Wiring harness

Related codes

Full explanation for 02
02E

Your boiler has stopped working because the water isn't moving through the system properly.

High DIY-safe £180-350

What to check first

  1. Check that your radiator valves are open
  2. Ensure the system pressure is between 1 and 1.5 bar on the pressure gauge
  3. Gently bleed your radiators to remove any trapped air

Parts commonly replaced

  • Circulation Pump
  • Pump Capacitor
  • Main PCB

Related codes

Full explanation for 02E
03E

Your boiler is unable to detect the movement of water through the system, which is preventing it from heating up correctly.

High Engineer only £120-£220

Parts commonly replaced

  • Flow sensor
  • Flow switch
  • Wiring harness

Related codes

Full explanation for 03E
04

Your boiler has become too hot and has automatically shut down to prevent damage to the internal components.

High Engineer only £120-220

Parts commonly replaced

  • Overheat thermostat
  • Circulation pump
  • Main heat exchanger

Related codes

Full explanation for 04
04E

Your boiler is struggling to accurately measure the temperature of the water coming out of your taps, which usually means you will have no hot water.

Medium Engineer only £90-160

Parts commonly replaced

  • Domestic Hot Water (DHW) NTC Thermistor
  • Connecting wiring harness

Related codes

Full explanation for 04E
05E

Your boiler has stopped working because the fan that clears away waste gases is not running or communicating correctly with the main system.

High Engineer only £180-350

Parts commonly replaced

  • Fan motor
  • Air pressure switch
  • Main PCB

Related codes

Full explanation for 05E
06E

Your boiler has detected that the water in the central heating system is getting too hot and has shut down to protect itself.

High DIY-safe £90-180

What to check first

  1. Check that all radiator valves are fully open
  2. Ensure the boiler pressure is between 1.0 and 1.5 bar
  3. Check for any blockages in the system by bleeding the radiators
  4. Reset the boiler using the control knob

Parts commonly replaced

  • Central heating thermistor (NTC sensor)
  • Circulating pump
  • Overheat thermostat

Related codes

Full explanation for 06E
08E

Your boiler has detected that there is not enough water in the system to operate safely, causing it to shut down to prevent damage.

High DIY-safe £0-120

What to check first

  1. Locate the filling loop (usually a silver flexible hose) underneath your boiler.
  2. Slowly open the tap or handles on the filling loop to allow water into the system.
  3. Watch the pressure gauge and close the taps once the needle reaches between 1.0 and 1.5 bar.

Parts commonly replaced

  • Filling loop
  • Expansion vessel
  • Pressure relief valve
Full explanation for 08E
09E

Your boiler has got too hot and has shut itself down for safety purposes to prevent damage to the internal parts.

High DIY-safe £120-280

What to check first

  1. Check that all radiator valves are fully open
  2. Ensure your system water pressure is between 1 and 1.5 bar
  3. Switch the boiler off and on again to attempt a reset once it has cooled down

Parts commonly replaced

  • Overheat Thermostat
  • Circulation Pump
  • Main Heat Exchanger

Related codes

Full explanation for 09E
Showing 11–20 of 49
10E

Your boiler has too much water inside it, which has caused the system to shut down for safety.

High DIY-safe £80-180

What to check first

  1. Check that the filling loop valves are fully closed and not leaking water into the system
  2. Bleed water from a radiator using a bleed key to reduce the pressure
  3. Monitor the pressure gauge to ensure it returns to between 1.0 and 1.5 bar
  4. Press the reset button once the pressure has been lowered

Parts commonly replaced

  • Filling loop valve
  • Expansion vessel
  • Pressure relief valve (PRV)
Full explanation for 10E
12

Your boiler's internal thermometer that monitors water temperature for your heating has stopped working correctly, causing the system to shut down.

High Engineer only £90-160

Parts commonly replaced

  • NTC Heating Sensor
  • Sensor Wiring Harness
Full explanation for 12
13E

Your boiler's computer brain has encountered a glitch or software task failure that is preventing it from running properly.

High DIY-safe £250-450

What to check first

  1. Locate the reset button on the front control panel.
  2. Press and hold the reset button for 5 seconds.
  3. Wait 2 minutes for the boiler to reboot; if the code persists, turn the mains power off and back on.

Parts commonly replaced

  • Main Printed Circuit Board (PCB)
Full explanation for 13E
17

Your boiler has identified an electrical problem with the fan, which is preventing it from safely clearing away exhaust fumes.

High Engineer only £180-350

Parts commonly replaced

  • Fan motor
  • Printed Circuit Board (PCB)
  • Wiring harness
Full explanation for 17
21E

Your boiler has detected that the water coming back from your radiators is too hot and has shut down to protect itself.

High DIY-safe £90-180

What to check first

  1. Check that all radiator valves are fully open
  2. Ensure there are no obstructions around the boiler vents
  3. Reset the boiler using the control knob once the system has cooled down

Parts commonly replaced

  • CH Return NTC Sensor
  • Circulation Pump
  • Main Heat Exchanger

Related codes

Full explanation for 21E
22E

Your boiler has detected that the exhaust gases are getting too hot, so it has shut down to protect itself and ensure your safety.

High Engineer only £120-£350

Parts commonly replaced

  • Flue Thermistor
  • Heat Exchanger
  • Main PCB

Related codes

Full explanation for 22E
23E

Your boiler has detected a problem with the sensor that monitors exhaust gases, and it has shut down as a safety precaution.

High Engineer only £120-£200

Parts commonly replaced

  • Flue Gas NTC Sensor
  • Wiring Harness

Related codes

Full explanation for 23E
24E

Your boiler has stopped working because it cannot correctly read the temperature of the water returning from your radiators.

High Engineer only £90-160

Parts commonly replaced

  • Central heating return NTC sensor
  • Wiring harness
  • Main PCB

Related codes

Full explanation for 24E
25E

Your boiler has detected that the water inside the main heating unit has likely frozen due to extremely cold weather, preventing it from operating safely.

High DIY-safe £0-120

What to check first

  1. Check if the external condensate pipe is frozen and thaw it using warm (not boiling) water.
  2. Increase the room thermostat and ensure the loft insulation around the boiler is adequate.
  3. Reset the boiler after the house has warmed up to see if the code clears.

Parts commonly replaced

  • None (thawing required)
  • Main Heat Exchanger
  • Condensate pipe insulation

Related codes

Full explanation for 25E
28

Your boiler has detected that there is not enough water circulating through the system or the pressure is too low to operate safely.

High DIY-safe £120-280

What to check first

  1. Check the pressure gauge on the front of the boiler; it should be between 1 and 1.5 bar.
  2. If the pressure is low, use the external filling loop to top up the water level.
  3. Check that all radiator valves are open and that the pump is not making loud banging noises.

Parts commonly replaced

  • Low water pressure switch
  • Circulation pump
  • Expansion vessel recharge

Related codes

Full explanation for 28
Showing 21–30 of 49
29E

Your boiler has stopped providing hot water because the hot water sensor has detected an unusually high temperature.

High Engineer only £90-180

Parts commonly replaced

  • DHW Temperature Sensor (NTC Thermistor)
  • DHW Heat Exchanger
  • Diverter Valve
Full explanation for 29E
30

Your boiler has sensed that the exhaust gases are getting too hot, so it has shut down as a safety precaution to prevent internal damage.

High Engineer only £120-280

Parts commonly replaced

  • Flue Thermistor
  • Heat Exchanger
  • Main PCB
Full explanation for 30
31

Your boiler has detected that the exhaust gases are not at the correct temperature, causing the system to shut down for safety.

High Engineer only £120-£200

Parts commonly replaced

  • Flue Gas NTC Sensor
  • Wiring Harness
  • Main Heat Exchanger (if scaled)

Related codes

Full explanation for 31
31E

Your boiler has lost its connection with your digital thermostat or smart control system, meaning they can no longer talk to each other to manage your heating.

High Engineer only £90-250

Parts commonly replaced

  • OpenTherm Interface Module
  • Digital Room Thermostat
  • Main PCB
Full explanation for 31E
41E

Your boiler has detected that water is not circulating correctly through the system, causing a heat imbalance.

High DIY-safe £150-350

What to check first

  1. Check that all radiator valves are fully open
  2. Check that the boiler pressure is between 1 and 1.5 bar on the gauge
  3. Bleed your radiators to remove trapped air

Parts commonly replaced

  • Circulation pump
  • Flow and return thermistors
  • Main heat exchanger (flushing)
Full explanation for 41E
42E

Your boiler has detected an unusual temperature difference between internal sensors, suggesting a possible blockage or circulation issue.

High Engineer only £120-£250

Parts commonly replaced

  • NTC Temperature Sensor
  • Circulation Pump
  • Main Heat Exchanger

Related codes

Full explanation for 42E
44E

Your boiler has detected an unusual temperature difference between internal sensors, suggesting that water is not circulating correctly through the system.

High Engineer only £120-£350

Parts commonly replaced

  • Circulation Pump
  • NTC Temperature Sensor
  • Main Heat Exchanger

Related codes

Full explanation for 44E
46E

Your boiler has lost the ability to monitor its own water pressure, meaning it has shut down to prevent damage.

High Engineer only £120-220

Parts commonly replaced

  • Water pressure sensor
  • Sensor wiring harness

Related codes

Full explanation for 46E
E02

Your boiler has stopped heating up because the water is not being pumped around the system correctly.

High Engineer only £180-350

Parts commonly replaced

  • Circulating Pump
  • Flow Switch
  • Main PCB

Related codes

Full explanation for E02
E03

Your boiler has detected an issue with the sensor that monitors water movement, meaning it cannot safely regulate the temperature and has shut down.

High Engineer only £120-220

Parts commonly replaced

  • Flow sensor
  • Wiring harness
  • Main PCB

Related codes

Full explanation for E03
Showing 31–40 of 49
E04

Your boiler's temperature sensor for hot water has stopped working, which means the system cannot tell how hot the water is and will likely stop providing it to your taps.

Medium Engineer only £90-160

Parts commonly replaced

  • DHW thermistor (NTC sensor)
  • Sensor wiring harness

Related codes

Full explanation for E04
E05

Your boiler has stopped working because the fan that removes waste gases is not spinning correctly or communicating with the control board.

High Engineer only £180-350

Parts commonly replaced

  • Fan motor
  • Air pressure switch
  • Main PCB

Related codes

Full explanation for E05
E06

Your boiler has detected that the water inside the heating system is getting too hot and has shut down as a safety precaution.

High Engineer only £90-180

Parts commonly replaced

  • CH Thermistor (NTC Sensor)
  • Internal Pump
  • Main Heat Exchanger

Related codes

Full explanation for E06
E08

Your boiler has stopped working because the water pressure in the system is too low and needs to be topped up.

High DIY-safe £0-120

What to check first

  1. Locate the silver filling loop (braided hose) usually found underneath the boiler.
  2. Gradually open the one or two small valves on the loop until you hear water entering.
  3. Monitor the pressure gauge and close the valves tightly once the needle reaches 1.5 bar.

Parts commonly replaced

  • Filling loop valve
  • Expansion vessel
  • Pressure sensor

Related codes

Full explanation for E08
E09

Your boiler has sensed that it is becoming too hot and has shut itself down to prevent damage to the internal components.

High DIY-safe £100-280

What to check first

  1. Check that all radiator valves are fully open to allow water to circulate
  2. Ensure there is enough water pressure in the system by checking the pressure gauge
  3. Allow the boiler to cool down for 20 minutes and then press the reset button

Parts commonly replaced

  • Overheat Thermostat
  • Circulation Pump
  • Main Heat Exchanger Flush

Related codes

Full explanation for E09
E10

Your boiler has too much water in the system, which puts unnecessary stress on the pipes and internal components.

Medium DIY-safe £80-160

What to check first

  1. Check that the filling loop valves are fully closed
  2. Bleed water from a radiator using a bleed key to reduce pressure
  3. Monitor the pressure gauge until it returns to between 1.0 and 1.5 bar
  4. Reset the boiler if the fault code persists

Parts commonly replaced

  • Filling loop valve
  • Expansion vessel
  • Pressure relief valve

Related codes

Full explanation for E10
E13

Your boiler's internal computer has encountered a glitch or software failure that is preventing it from running correctly.

High DIY-safe £180-350

What to check first

  1. Turn the boiler off at the main electrical switch
  2. Wait for 30 seconds
  3. Turn the switch back on and press the 'Reset' button

Parts commonly replaced

  • Main Printed Circuit Board (PCB)
Full explanation for E13
E21

Your boiler has sensed that the water returning from your radiators is too hot, causing the system to shut down for protection.

High DIY-safe £100-220

What to check first

  1. Check that all radiator valves (TRVs) are fully open
  2. Ensure the boiler pressure is between 1.0 and 1.5 bar
  3. Restart the boiler using the reset button

Parts commonly replaced

  • CH Return NTC Sensor
  • Circulation Pump
  • Main PCB

Related codes

Full explanation for E21
E22

Your boiler has detected that the exhaust gases are getting too hot and has shut down as a safety precaution.

High Engineer only £120-£350

Parts commonly replaced

  • Flue Thermistor
  • Main Heat Exchanger
  • Circulation Pump

Related codes

Full explanation for E22
E23

Your boiler has detected a problem with the sensor that monitors exhaust gases, and it has shut down as a safety precaution.

High Engineer only £120-£210

Parts commonly replaced

  • Flue NTC sensor
  • Wiring harness connector

Related codes

Full explanation for E23
Showing 41–49 of 49
E24

Your boiler has detected a problem with the sensor that monitors water returning from your radiators, preventing it from heating your home properly.

High Engineer only £90-160

Parts commonly replaced

  • Central heating return NTC thermistor
  • Connecting wiring harness

Related codes

Full explanation for E24
E25

Your boiler's main internal unit has frozen due to extremely cold weather, preventing it from heating water safely.

High DIY-safe £60-120

What to check first

  1. Increase the room thermostat setting to encourage the pump to circulate water
  2. Slowly thaw any exposed external pipework using a hot water bottle or warm (not boiling) water
  3. Once thawed, reset the boiler using the control knob or reset button

Parts commonly replaced

  • None (Thawing often resolves it)
  • External pipe insulation (Lagging)

Related codes

Full explanation for E25
E29

Your boiler has detected that the hot water temperature has become too high, causing it to shut down for safety.

High Engineer only £90-180

Parts commonly replaced

  • DHW NTC thermistor (temperature sensor)
  • Diverter valve
  • Main heat exchanger

Related codes

Full explanation for E29
E31

Your boiler is having trouble talking to your smart thermostat or external controls, meaning they cannot tell the boiler when to turn on or off.

High DIY-safe £80-220

What to check first

  1. Check that your smart thermostat or wall controller is powered on and has working batteries.
  2. Ensure the wires leading from your thermostat to the boiler haven't been accidentally bumped or damaged.
  3. Restart the boiler using the reset button to see if it re-establishes a connection.

Parts commonly replaced

  • OpenTherm Interface Module
  • Smart Thermostat receiver
  • Control PCB
Full explanation for E31
E41

Your boiler has sensed that the water temperatures leaving and returning to the unit are too far apart, which usually means water isn't moving through the system properly.

High DIY-safe £120-350

What to check first

  1. Check that all radiator valves are fully open
  2. Ensure the boiler pressure is between 1.0 and 1.5 bar
  3. Bleed all radiators to remove trapped air bubbles

Parts commonly replaced

  • Circulation pump
  • Flow and return thermistors
  • Main heat exchanger (flushing debris)

Related codes

Full explanation for E41
E42

Your boiler has detected that its two temperature sensors are giving very different readings, suggesting water isn't flowing correctly or a sensor has failed.

High Engineer only £90-180

Parts commonly replaced

  • NTC Temperature Sensor
  • Internal Wiring Harness
  • Circulation Pump

Related codes

Full explanation for E42
E43

Your boiler has detected an unusual temperature difference between internal sensors, suggesting a problem with how water is moving through the system.

High Engineer only £120-280

Parts commonly replaced

  • NTC Temperature Sensors
  • Circulation Pump
  • Main Control Board

Related codes

Full explanation for E43
E44

Your boiler has sensed a confusing temperature reading between its internal sensors and has shut down as a safety precaution.

High Engineer only £120-280

Parts commonly replaced

  • NTC Temperature Sensor
  • Main PCB
  • Circulation Pump

Related codes

Full explanation for E44
E46

Your boiler has lost track of its internal water pressure, meaning it cannot confirm if it is safe to run and has likely stopped working as a result.

High Engineer only £120-190

Parts commonly replaced

  • Water Pressure Sensor
  • Sensor Wiring Loom

Related codes

Full explanation for E46