Verified boiler fault code
ATAG 105 Fault Code (i-Range (2019 and newer))
Flow check failed three times (flow-check sequence 1, 3 or 4; last check 3).
Safety disclaimer
Fault code summary
- Manufacturer
- ATAG
- Fault code
- 105
- Fault type
- Circulation, Flow sensor
- Severity
- Not specified
- Reset
- ATAG distinguishes blocking codes from error codes; a locked boiler may require reset and/or service intervention.
- Applicable models
- ATAG iC, ATAG iS, ATAG iR
Quick answer
Flow check failed three times (flow-check sequence 1, 3 or 4; last check 3).
What does this fault code mean?
Flow check failed three times (flow-check sequence 1, 3 or 4; last check 3).
Common causes
- Flow check failed three times.
Symptoms
- The ATAG display shows error code 105.
What can the homeowner safely check?
- Record the code and contact the installer.
Boiler reset information
ATAG distinguishes blocking codes from error codes; a locked boiler may require reset and/or service intervention.
When should I call an engineer?
Contact a suitably qualified heating engineer when the fault persists, the boiler locks out, or the manufacturer instructions do not resolve it. For gas appliance work in the UK, use a Gas Safe registered engineer.
Engineer diagnosis
- Investigate flow, pump operation and flow-check sensing.
Applicable boiler models
Related fault codes
- 101 — i-Range (2019 and newer)
Overheat.
Read fault code - 102 — i-Range (2019 and newer)
Pressure sensor error.
Read fault code - 103 — i-Range (2019 and newer)
Flow check failed three times (flow-check sequence 1, 3 or 4; last check 1).
Read fault code - 104 — i-Range (2019 and newer)
Flow check failed.
Read fault code - 106 — i-Range (2019 and newer)
Flow check failed three times (flow-check sequence 1, 3 or 4; last check 4).
Read fault code - 107 — i-Range (2019 and newer)
Flow check 5 failed.
Read fault code - 108 — i-Range (2019 and newer)
Pressure below Pmin (less than 0.5 bar); filling is needed.
Read fault code - 109 — i-Range (2019 and newer)
Pressure above Pmax.
Read fault code
Manufacturer documentation
ATAG - Boiler Troubleshooting2019 & newer range: 105 — Flow Check Failed 3 times (1 or 3 or 4, last 3).
Last verified
2026-09-12
Frequently asked questions
What does ATAG 105 mean?
Flow check failed three times (flow-check sequence 1, 3 or 4; last check 3).
Can I reset a ATAG 105 fault?
ATAG distinguishes blocking codes from error codes; a locked boiler may require reset and/or service intervention.