105 error code
ATAG 105 error code – Flow check failed three times; last failure check 3
What does ATAG ATAG iC, iS and iR boiler range — 2019 and newer 105 mean?
ATAG identifies code 105 as: Flow check failed three times; last failure check 3.
The code identifies the condition detected by the product; it does not always identify the failed component on its own. Confirm the full code and exact model before ordering parts or attempting a reset.
The ATAG ATAG iC, iS and iR boiler range — 2019 and newer 105 error code indicates aTAG identifies code 105 as: Flow check failed three times; last failure check 3. This guide explains what the code means, the symptoms and likely causes, the checks that are safe to make, and when to stop and arrange an authorised repair.
Symptoms you may notice
The boiler did not confirm the water-flow or pump response required for safe operation.
Common causes
Low pressure, air, restricted circulation, pump fault, flow-switch fault, closed valve or sensor problem.
Before you start troubleshooting
Use the display, rating label or product menu to confirm the exact model. Similar-looking codes can have different meanings across product generations and regions.
- Record the complete code before switching the equipment off.
- Check only user-accessible controls, filters and external connections described in the manual.
- Do not open gas, refrigerant, combustion or electrical compartments.
Troubleshooting steps
Check visible pressure and that user-operated heating valves are open. Internal pump, flow-switch and hydraulic checks require a qualified engineer.
Can you fix this error code yourself?
The safest next step depends on the exact model and the cause behind the code. External checks may help, but a returning fault needs professional diagnosis.
A successful reset is not proof that the underlying issue is fixed. If 105 reappears, note when it happens and give that information to the service engineer.
Reset instructions
Reset a locked boiler only as described in the ATAG user manual and only after safe external checks. Temporary blocking codes may clear automatically. Do not repeatedly reset a returning fault.
Applicable products and models
ATAG iC, iS and iR boiler range — 2019 and neweriC; iS; iR; iC Economiser2019 onwardWhen to contact a professional
Contact ATAG or a Gas Safe registered engineer when the code persists, the boiler locks again, pressure will not remain stable, or internal component testing is required.
Frequently asked questions
What does ATAG ATAG iC, iS and iR boiler range — 2019 and newer 105 mean?
ATAG identifies code 105 as: Flow check failed three times; last failure check 3.
Can I fix ATAG ATAG iC, iS and iR boiler range — 2019 and newer 105 myself?
Some external checks may be suitable for the user, but the result depends on the exact model and cause. Use the official manual and arrange service if the code returns.
Should I reset the product after code 105?
Reset a locked boiler only as described in the ATAG user manual and only after safe external checks. Temporary blocking codes may clear automatically. Do not repeatedly reset a returning fault.
When should I arrange a repair?
Contact ATAG or a Gas Safe registered engineer when the code persists, the boiler locks again, pressure will not remain stable, or internal component testing is required.