BoilerFaultCodes.com

Atag Boiler Fault Codes

Oil Natural Gas

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Most common fault codes

1P4
Your boiler has detected that the water pressure is too low and needs a top-up to continue working safely.
May be DIY safe · £0-80
20
Your boiler has lost track of the water temperature leaving the unit, which means it will stop working to prevent overheating.
Gas Safe engineer required · £120-220
40
Your boiler has stopped working because it cannot correctly measure the temperature of the water returning from your radiators.
Gas Safe engineer required · £120-220

All 28 fault codes

Code Severity Plain English
1P4 High Your boiler has detected that the water pressure is too low and needs a top-up to continue working safely.
10 Low Your boiler has lost communication with the sensor that monitors the outdoor temperature, which may cause your heating to behave unpredictably.
20 High Your boiler has lost track of the water temperature leaving the unit, which means it will stop working to prevent overheating.
40 High Your boiler has stopped working because it cannot correctly measure the temperature of the water returning from your radiators.
61 High Your boiler's internal components have stopped communicating with each other, meaning the central control unit cannot send or receive the signals needed to heat your home.
78 High Your boiler has stopped working because the water pressure is either too high or too low to operate safely.
101 High Your boiler has switched itself off because it has become too hot internally, usually due to a lack of water flow or a blockage.
102 High Your boiler has lost its ability to accurately measure the water pressure required to run, which often causes the system to stop working for safety.
104 High Your boiler has detected that water is not circulating correctly through the system, causing it to shut down for safety.
105 Low Your boiler is simply running an automatic air-removal cycle after being switched off or experiencing a brief power cut.
108 High Your boiler has stopped working because the water pressure is too low and needs to be topped up.
109 Emergency Your boiler has shut down because the internal water pressure has become too high, which could potentially cause leaks or damage if not addressed.
110 High Your boiler has reached an unsafe temperature and has shut down to protect its internal components and your home's pipework.
111 Emergency Your boiler has detected too much water pressure in the system, which can cause internal damage or leaks if not addressed.
112 High Your boiler has stopped working because a sensor that monitors the temperature of the water returning to the unit has likely failed.
114 Low Your boiler is having trouble reading the outside temperature, which may cause your heating to respond inefficiently to the weather.
119 High Your boiler has detected that a vital internal electrical connection is missing or has come loose, preventing it from operating.
129 High Your boiler has stopped working because the internal fan, which clears away waste gases, is unable to spin or start up.
133 High Your boiler has tried to light several times but has been unable to produce a flame, meaning your heating and hot water will not work.
141 High Your boiler has stopped working because it cannot detect water moving through the system to heat your radiators.
151 High Your boiler has detected a problem with the fan or its internal control chip, meaning it cannot safely clear waste gases and will not start.
154 High Your boiler has detected that water is moving too slowly or in the wrong direction through the system, causing the pipes to heat up unevenly.
201 Medium Your boiler's hot water sensor has stopped working correctly, meaning your taps might not deliver hot water as expected.
203 High Your boiler is struggling to detect the temperature of your hot water cylinder, which usually means the system cannot heat your water correctly.
303 High Your boiler's internal computer has encountered a fault and is unable to communicate with the rest of the system.
304 Medium Your boiler has been manually reset too many times in a short period and has locked itself as a safety precaution.
501 High Your boiler is failing to light the gas flame required to heat your water and radiators.
612 High The built-in fan that safely clears exhaust gases out of your home is not spinning, causing your boiler to shut down for safety.

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