Atag Q 30CR Fault codes & diagnostics

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

Combi Natural Gas 30 kW 2013-2018 Discontinued

Replaced by: i32C

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.
1 Emergency 16 High 7 Medium 8 Low
Just want the most common Atag Q 30CR faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 32 documented codes

Tap any card for details

LED / flash-pattern codes
FILL (flashing)

Your boiler has detected that the water pressure inside your heating system is too low and needs to be topped up to function correctly.

Medium DIY-safe

What to check first

  1. Locate the external filling loop (a flexible metal or silver hose connected between two pipes under your boiler).
  2. Open the valves on both ends of the hose slowly to allow water into the system.
  3. Watch the pressure gauge on the boiler front until the needle reaches the green zone (usually 1.5 bar), then turn both valves securely off.

Parts commonly replaced

  • Filling loop
  • Pressure relief valve
  • Expansion vessel
Full explanation for FILL (flashing)
Digital codes
Block 01

Your boiler has been automatically shut down because an external safety device, such as a frost thermostat or a heat link, has triggered a signal to stop the system.

High Engineer only £120-250

Parts commonly replaced

  • External frost stat
  • External controls interface
  • Wiring connection
Full explanation for Block 01
Block 11

Your boiler has paused the heating because it cannot move water through your radiators fast enough, likely due to a blockage or closed valves.

Medium DIY-safe £120-£250

What to check first

  1. Check that all radiator valves throughout your home are fully open.
  2. Ensure your system pressure is set correctly, usually between 1.0 and 1.5 bar.
  3. Check for any signs of a stuck pump or sludge buildup in the system pipes.

Parts commonly replaced

  • Central heating pump
  • Flow/Return sensors
  • Plate heat exchanger

Related codes

Full explanation for Block 11
Block 12

Your boiler has detected that the water is not flowing or heating correctly while producing hot water, causing it to pause the hot water function to protect itself.

Medium Engineer only £150-300

Parts commonly replaced

  • Diverter valve
  • Plate heat exchanger
  • Flow sensor

Related codes

Full explanation for Block 12
Block 60

Your boiler’s internal computer settings have been incorrectly adjusted, which is preventing it from knowing how much power it should use to operate safely.

Medium Engineer only £120-200

Parts commonly replaced

  • Control Board (PCB)
  • Wiring harness
Full explanation for Block 60
Block 67

Your boiler has detected an unusual temperature difference while it is supposed to be switched off, so it is temporarily pausing to prevent any potential issues.

Medium Engineer only £120-250

Parts commonly replaced

  • Flow sensor
  • Return sensor
  • Main PCB
Full explanation for Block 67
Block 80

Your boiler has automatically stopped heating because the exhaust gases getting rid of your smoke and fumes are currently too hot.

High Engineer only £120-250

Parts commonly replaced

  • Flue gas sensor
  • Heat exchanger
  • Burner seal

Related codes

Full explanation for Block 80
Block 81

Your boiler has stopped working because it cannot detect a vital safety sensor that monitors the temperature of the gases leaving your home.

High Engineer only £120-220

Parts commonly replaced

  • Flue gas sensor
  • Wiring harness

Related codes

Full explanation for Block 81
Block 82

Your boiler has detected an electrical fault in a sensor that monitors exhaust gases and has safely shut down to prevent incorrect operation.

High Engineer only £150-250

Parts commonly replaced

  • Flue gas temperature sensor
  • Wiring harness

Related codes

Full explanation for Block 82
Showing 11–20 of 32
Block 85

Your boiler is currently running a self-cleaning air-removal cycle because it cannot detect water moving through the system properly.

High Engineer only £120-250

Parts commonly replaced

  • Central heating pump
  • Flow sensor
  • System diverter valve
Full explanation for Block 85
COdE

Your boiler is asking for a security or installer code instead of displaying a fault, meaning you have accidentally entered the configuration menu.

Low DIY-safe

What to check first

  1. Press the 'Reset' or 'Back' button on the control panel to exit the menu
  2. Wait 5 minutes for the display to time out and return to the home screen
  3. Switch the boiler off at the fused spur for 30 seconds and turn it back on
Full explanation for COdE
Err.L - Err.5

Your boiler is displaying a stored history of previous faults, which means it is currently referencing older issues rather than a single active problem.

Medium Engineer only £120-250

Parts commonly replaced

  • Main PCB
  • Wiring harness
Full explanation for Err.L - Err.5
Error 00

Your boiler is failing to light the internal flame properly, meaning it cannot produce heat or hot water.

High Engineer only £150-300

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Ionisation probe
Full explanation for Error 00
Error 01

Your boiler has detected an electrical fault in its internal control circuit, which has caused it to shut down to prevent further damage.

High Engineer only £150-300

Parts commonly replaced

  • Control board (PCB)
  • Wiring harness
  • External pump or fan

Related codes

Full explanation for Error 01
Error 02

Your boiler is failing to light the internal burner, which means it cannot produce any heat or hot water.

High Engineer only £150-300

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Ignition transformer

Related codes

Full explanation for Error 02
Error 04

Your boiler has lost its electrical connection or is struggling to process the power supply, causing it to shut down for protection.

High Engineer only £120-250

Parts commonly replaced

  • Printed circuit board
  • Wiring harness
  • Power supply module
Full explanation for Error 04
Error 05

Your boiler is struggling to accurately adjust its internal settings, which means it has paused operation to prevent any potential damage.

High Engineer only £120-250

Parts commonly replaced

  • Control PCB
  • Gas valve

Related codes

Full explanation for Error 05
Showing 21–30 of 32
Error 12

Your boiler has stopped working because an internal electrical safety fuse has blown, preventing the system from powering up safely.

High Engineer only £120-220

Parts commonly replaced

  • 3A T fuse
  • PCB (Printed Circuit Board)
Full explanation for Error 12
Error 18

Your boiler has detected that the water inside the system has become dangerously hot and has shut itself down to prevent damage.

High Engineer only £150-£300

Parts commonly replaced

  • NTC temperature sensor
  • Central heating pump
  • Heat exchanger
Full explanation for Error 18
Error 19

Your boiler has detected that the water returning to it from your radiators is getting too hot, so it has shut down to prevent damage.

High Engineer only £150-300

Parts commonly replaced

  • NTC temperature sensor
  • Central heating pump
  • Plate heat exchanger
Full explanation for Error 19
Error 28

Your boiler has stopped working because it cannot detect that the internal fan is spinning, which is necessary for safe operation.

High Engineer only £180-350

Parts commonly replaced

  • Fan assembly
  • Wiring harness
  • PCB
Full explanation for Error 28
Error 69

Your boiler's electronic control panel is not receiving power or is failing to communicate, meaning the boiler has completely shut down and cannot be operated.

High Engineer only £150-350

Parts commonly replaced

  • Control PCB
  • Display interface unit
  • Wiring harness
Full explanation for Error 69
Error 80

Your boiler has detected that the gases venting out of your flue are getting dangerously hot and has shut itself down to prevent damage or overheating.

Emergency Engineer only £150-350

Parts commonly replaced

  • Flue gas sensor
  • Heat exchanger
  • Primary flow sensor
Full explanation for Error 80
FILL

Your boiler has lost water pressure and needs to be topped up to work at full capacity again.

Medium DIY-safe

What to check first

  1. Locate the external filling loop, which is a silver braided hose near the boiler
  2. Open the small valve or tap on the loop to let water into the system
  3. Watch the pressure gauge on the boiler screen until it reaches 1.5 bar
  4. Close the valve tightly and check for leaks

Parts commonly replaced

  • Filling loop
  • Pressure sensor
Full explanation for FILL
HIGH

Your boiler has too much water inside the system, causing the pressure to rise above the safe limit.

High DIY-safe

What to check first

  1. Locate a radiator anywhere in your house.
  2. Open the bleed valve on the radiator using a radiator key to let water out.
  3. Place a container underneath to catch the water and watch the boiler pressure gauge.
  4. Close the valve once the pressure drops into the green zone (usually around 1.5 bar).

Parts commonly replaced

  • Pressure relief valve
  • Pressure sensor/transducer
Full explanation for HIGH
P x.x

Your boiler is simply displaying the current water pressure reading, which is a normal status update rather than a fault.

Low DIY-safe

What to check first

  1. Check the display periodically to ensure the pressure stays between 1.0 and 1.5 bar
  2. If the pressure is below 1.0 bar, use the filling loop to top it up
  3. If the pressure is above 2.0 bar, bleed a radiator to release air and lower the pressure
Full explanation for P x.x
Showing 31–32 of 32
StBY

Your boiler is currently in standby mode and is working exactly as it should, waiting for a signal from your thermostat or hot water tap to start operating.

Low DIY-safe

What to check first

  1. Check your room thermostat is set to a higher temperature than the current room temperature
  2. Ensure your heating timer or programmer is set to 'On'
  3. Turn on a hot water tap to see if the boiler fires up
Full explanation for StBY
STOP

Your boiler has successfully finished being topped up with water and is ready to work again.

Low DIY-safe

What to check first

  1. Check the boiler display to ensure the STOP message has cleared
  2. Close the filling loop valve tightly
  3. Restart the boiler using the reset button if it does not resume normal operation automatically
Full explanation for STOP