Atag iR Regular Fault codes & diagnostics

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

Regular Natural GasLPG 2015 onwards Discontinued
GC Numbers 41-310-3241-310-3341-310-3441-310-3541-310-3641-310-3741-310-3841-310-3941-310-4041-310-41
Download the Atag iR Regular manual The official installation & service manual (PDF) — the exact document these fault codes were verified against. PDF

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 19 High 4 Low
Versions & GC numbers

Which version do you have?

The GC number on your boiler's data badge identifies the exact appliance and production years, as recorded in the UK Product Characteristics Database.

GC number Appliance (register name) Produced
41-310-32 iR15 2015–present
41-310-34 iR18 2015–present
41-310-36 iR24 2015–present
41-310-38 iR32 2015–present
41-310-40 iR40 2015–present
Just want the most common Atag iR Regular faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 24 documented codes

Tap any card for details

1P4

Your boiler has detected that the water pressure is getting low and needs to be topped up to keep the system running correctly.

Low DIY-safe £0-80

What to check first

  1. Locate the external filling loop, which is usually a silver flexible hose with one or two small taps.
  2. Slowly open the tap(s) until you hear water flowing into the system.
  3. Watch the pressure gauge on the boiler until it reaches between 1.2 and 1.5 bar, then close the taps tightly.

Parts commonly replaced

  • None (Filling loop adjustment only)
  • External filling loop

Related codes

Full explanation for 1P4
10

Your boiler is having trouble reading the temperature outside, which helps it decide how hard it needs to work to heat your home.

Low Engineer only £90-160

Parts commonly replaced

  • Outside weather compensation sensor
  • Sensor wiring

Related codes

Full explanation for 10
20

Your boiler has stopped heating because it is unable to accurately measure the temperature of the water leaving the unit.

High Engineer only £120-£210

Parts commonly replaced

  • Flow NTC temperature sensor
  • Wiring harness
  • Control PCB

Related codes

Full explanation for 20
40

Your boiler has detected an issue with the sensor that monitors water returning from your radiators, causing the system to stop running for safety.

High Engineer only £90-160

Parts commonly replaced

  • Return NTC thermistor
  • Wiring harness
  • Control PCB

Related codes

Full explanation for 40
50

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

High Engineer only £120-210

Parts commonly replaced

  • DHW NTC temperature sensor (T3)
  • Sensor wiring harness

Related codes

Full explanation for 50
61

Your boiler has lost its internal connection to the main control board, meaning it cannot receive the commands needed to fire up and heat your home.

High Engineer only £120-450

Parts commonly replaced

  • Main PCB (Control Board)
  • Wiring Harness
  • Display PCB

Related codes

Full explanation for 61
78

Your boiler has detected that the water pressure is either too low or too high for it to run safely, or there is a problem with the sensor that measures this pressure.

High DIY-safe £80-180

What to check first

  1. Check the pressure gauge on your system, which should ideally be between 1.0 and 1.5 bar when the system is cold.
  2. If the pressure is below 1.0 bar, use the external filling loop valves to top up the water pressure.
  3. If the pressure is above 3.0 bar, you may need to bleed a radiator to release the excess pressure.
  4. Reset the boiler once the correct pressure is reached.

Parts commonly replaced

  • Water pressure sensor
  • Expansion vessel recharge/replacement
  • Filling loop

Related codes

Full explanation for 78
101

Your boiler has become too hot and has shut down as a safety precaution to prevent damage.

High DIY-safe £100-350

What to check first

  1. Check that all radiator valves are fully open and not turned off.
  2. Ensure the external heating pump is running and hasn't become stuck.
  3. Wait for the boiler to cool down and press the 'Reset' button.

Parts commonly replaced

  • External Circulation Pump
  • Overheat Thermostat
  • NTC Temperature Sensor

Related codes

Full explanation for 101
102

Your boiler is having trouble monitoring its internal water pressure, which prevents it from running safely.

High Engineer only £120-£210

Parts commonly replaced

  • Pressure sensor
  • Wiring harness
  • Main PCB

Related codes

Full explanation for 102
104

Your boiler has detected that water is not circulating properly through the unit, causing it to shut down for safety.

High DIY-safe £120-£350

What to check first

  1. Check that your system pressure is between 1.0 and 1.5 bar on the pressure gauge.
  2. Ensure all radiator valves are fully open and any zone valves are functioning.
  3. Try bleeding your radiators to remove any trapped air that could be blocking water flow.
  4. Reset the boiler once you have checked the water pressure and valves.

Parts commonly replaced

  • Circulation pump
  • Flow/Return thermistors
  • Main heat exchanger (flushing service)

Related codes

Full explanation for 104
Showing 11–20 of 24
105

Your boiler is currently running an automatic air-purging sequence to clear air from the system following a power cut or being switched back on.

Low DIY-safe £0

What to check first

  1. Wait approximately 7 to 10 minutes for the automatic venting process to complete.
  2. Check that your radiators are bled and the system pressure is between 1.0 and 1.5 bar.
  3. Ensure the boiler power supply is stable and not being interrupted by a loose plug or tripped fuse.

Related codes

Full explanation for 105
108

Your boiler has detected that the water pressure is too low to operate safely, meaning it needs more water added to the system.

High DIY-safe £0-120

What to check first

  1. Locate the external filling loop, which is usually a flexible silver hose with one or two small taps.
  2. Slowly open the tap(s) until you hear water flowing and the pressure gauge reaches between 1.0 and 1.5 bar.
  3. Close the tap(s) tightly and restart the boiler to clear the fault code.

Parts commonly replaced

  • External filling loop
  • Expansion vessel
  • Pressure sensor

Related codes

Full explanation for 108
109

Your boiler has detected that the water pressure inside the system is too high, causing it to shut down to prevent damage.

Emergency DIY-safe £80-160

What to check first

  1. Check the filling loop valves are tightly closed
  2. Bleed a radiator using a bleed key to release excess water and pressure
  3. Monitor the pressure gauge until it returns to between 1.0 and 1.5 bar

Parts commonly replaced

  • Filling loop
  • Expansion vessel
  • Pressure sensor

Related codes

Full explanation for 109
110

Your boiler has shut down because it detected it was getting too hot or a temperature sensor has failed.

High DIY-safe £90-220

What to check first

  1. Check that your radiator valves are open to allow water to flow.
  2. Ensure your system pressure is topped up to between 1.0 and 1.5 bar.
  3. Wait 15 minutes for the unit to cool down, then press the 'Reset' button.

Parts commonly replaced

  • NTC Temperature Sensor
  • Circulation Pump
  • Main Heat Exchanger cleaning

Related codes

Full explanation for 110
112

Your boiler has stopped working because the internal sensor that monitors the temperature of the water returning to the unit has developed a fault.

High Engineer only £120-£190

Parts commonly replaced

  • Return NTC thermistor sensor
  • Wiring harness

Related codes

Full explanation for 112
114

Your boiler has lost connection with the sensor that measures the temperature outside, meaning it cannot automatically adjust its efficiency based on the weather.

Low Engineer only £90-160

Parts commonly replaced

  • External weather compensation sensor
  • Sensor wiring

Related codes

Full explanation for 114
140

Your boiler has stopped working because it cannot detect the water movement it expects when the pump starts up.

High DIY-safe £180-450

What to check first

  1. Check that your home's main water stopcock and all boiler valves are fully open
  2. Ensure all radiator valves (TRVs) are turned to their highest setting
  3. Check the boiler pressure gauge and top up to 1.5 bar if it is too low
  4. Restart the boiler using the reset button to see if the fault clears

Parts commonly replaced

  • Circulation pump
  • Water pressure sensor
  • PCB (Main Control Board)

Related codes

Full explanation for 140
151

Your boiler has stopped working because the internal fan, which safely exhausts fumes, isn't spinning at the correct speed.

High Engineer only £250-450

Parts commonly replaced

  • Fan assembly
  • Control PCB
  • Wiring harness

Related codes

Full explanation for 151
201

Your boiler's temperature sensor for hot water has developed a fault, meaning the system cannot accurately measure or provide hot water.

High Engineer only £90-160

Parts commonly replaced

  • DHW Temperature Sensor (NTC)
  • Sensor wiring harness

Related codes

Full explanation for 201
203

Your boiler has lost connection with the sensor that monitors the temperature in your hot water tank, meaning it cannot heat your water correctly.

High Engineer only £90-180

Parts commonly replaced

  • Hot water cylinder NTC sensor (probe)
  • Sensor wiring harness

Related codes

Full explanation for 203
Showing 21–24 of 24
303

Your boiler's main control board has experienced a communication error or internal failure, meaning the system can no longer manage its functions safely.

High Engineer only £350-£550

Parts commonly replaced

  • Main PCB (Printed Circuit Board)
  • Wiring harness

Related codes

Full explanation for 303
304

Your boiler has been manually reset too many times in a short period and has locked itself out as a safety precaution.

High DIY-safe £0-120

What to check first

  1. Turn the boiler power off at the fused spur switch (the wall switch).
  2. Wait for at least 30 seconds.
  3. Turn the power back on to clear the temporary software lock.

Parts commonly replaced

  • No parts usually required
  • Ignition Electrode
  • Spark Cable

Related codes

Full explanation for 304
501

Your boiler is not lighting properly, meaning it cannot produce heat or hot water because the flame is not being detected.

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. Inspect the condensate pipe (the white plastic pipe outside) for ice blockages if it is freezing weather.
  3. Try resetting the boiler using the 'Reset' button.

Parts commonly replaced

  • Ignition electrode
  • Ionisation probe
  • Gas valve

Related codes

Full explanation for 501
612

Your boiler has stopped working because the internal fan, which safely exhausts fumes, is unable to spin or start up.

High Engineer only £250-£450

Parts commonly replaced

  • Extraction Fan
  • Fan Wiring Harness
  • Main Control PCB

Related codes

Full explanation for 612