ATAG Fault Codes

Select a fault code to see its meaning, common causes and how to fix it.

10 Fault code 10 on ATAG boilers signals a problem with the outdoor temperature sensor. The boiler expects to read a valid… Read more →
101 Fault code 101 on an ATAG boiler signals that the unit has detected — or suspects it has detected — an over-temperature… Read more →
102 Fault code 102 on ATAG boilers signals that the boiler's control system has detected a problem with the water pressure… Read more →
104 Fault code 104 on an Atag boiler indicates that the system water pressure has dropped below 1 bar, or that the boiler's… Read more →
105 Fault code 105 on an Atag boiler points to a problem with the condensate drainage system — typically a blocked or… Read more →
108 Fault code 108 on an ATAG boiler — sometimes displayed as 1P4 or F1P4 — signals that the water pressure inside the… Read more →
109 Error code 109 on an ATAG boiler is a pressure-related fault from the 100-series group. There is a genuine ambiguity… Read more →
110 Fault code 110 on an ATAG boiler indicates that the appliance has detected an unsafe condition — either the water… Read more →
111 ATAG fault code 111 indicates that the boiler has detected a water temperature above its maximum permitted threshold… Read more →
112 Fault code 112 on an Atag boiler indicates a problem with the return temperature sensor, also known as the T2 or NTC… Read more →
114 Fault code 114 on an ATAG boiler indicates that the boiler's outdoor temperature sensor is not behaving as expected.… Read more →
117 Fault code 117 on an Atag boiler means the system water pressure has climbed above 3 bar, triggering a safety lockout.… Read more →
118 Fault code 118 on an Atag boiler signals that the central heating system pressure has dropped too low — typically below… Read more →
119 Fault code 119 on Atag boilers indicates that the control board (PCB) cannot detect the required link — sometimes… Read more →
129 Fault code 129 on ATAG boilers indicates that the boiler's fan has failed to start up. When the fan cannot spin up to… Read more →
133 Fault code 133 means your Atag boiler has tried to light itself five times in a row and failed to detect a stable flame… Read more →
141 Fault code 141 on an ATAG boiler indicates that the central heating flow switch is reading as open. The flow switch is… Read more →
151 Fault code 151 on an Atag boiler indicates that the fan speed has fallen outside the acceptable tolerance for at least… Read more →
154 ATAG fault code 154 indicates that the boiler has detected an abnormal temperature condition: the return water… Read more →
1P1 The 1P1 fault code appears on Atag i Series boilers when the control system detects that the flow water temperature is… Read more →
1P2 The 1P2 code is a safety lockout triggered when the boiler detects that the temperature difference between its flow… Read more →
1P3 The ATAG 1P3 fault code indicates a repeated 'Flow Check Failed' condition. Specifically, it is triggered when the… Read more →
1P4 The 1P4 fault code on an Atag boiler (also displayed as F1P4 or fault code 108) indicates that the system water… Read more →
20 Fault code 20 on an ATAG boiler signals that the boiler's control system has detected a problem with the flow sensor,… Read more →
201 Fault code 201 on an Atag boiler indicates that the T3 NTC thermistor — the temperature sensor responsible for… Read more →
203 Fault code 203 on an Atag boiler indicates that the boiler's control system has detected a problem with the tank probe… Read more →
303 Fault code 303 on an Atag boiler signals a problem with the PCB (Printed Circuit Board) — the central control unit that… Read more →
304 Fault code 304 on ATAG boilers (including the iC, iS, and iR ranges) means the boiler has been reset too many times… Read more →
40 ATAG fault code 40 points to a problem with the boiler's return thermistor — the small temperature sensor that monitors… Read more →
50 Fault code 50 on ATAG iC-Range combi boilers indicates a problem with the domestic hot water (DHW) temperature sensor,… Read more →
501 Fault code 501 on an ATAG boiler means the appliance has tried to ignite and establish a flame multiple times —… Read more →
61 Fault code 61 on an ATAG boiler signals that the boiler's internal monitoring has detected a problem with water flow… Read more →
612 Fault code 612 on Atag boilers (including the iC, iS, and iR ranges) indicates that the boiler's fan has failed to… Read more →
78 Fault code 78 appears on ATAG boilers when the system water pressure has dropped below 1 bar, or when the boiler's… Read more →