Central heating flow switch is open
The 141 error code on Atag boilers indicates central heating flow switch is open.
Atag 141 means: central heating flow switch is open. On this component the documented failure modes are wiring, connector or harness of the flow switch damaged or loose, flue or air intake blocked or restricted or the flow switch has failed — short circuit or open circuit. You can safely reset the boiler once — if 141 returns, do not keep resetting. A qualified heating engineer should diagnose the root cause.
What Does 141 Mean
The 141 code is shown by the boiler’s control board when it detects central heating flow switch is open. The boiler then stops instead of continuing to run in that condition: the code is the appliance reporting a problem, not proof that the boiler is broken.
| What you see on the boiler |
|---|
| The display shows 141 and the boiler stops until the fault is cleared |
Common Causes
The manufacturer does not publish a cause list for this specific code. The causes below are the failure modes documented for the same component on other boilers, confirmed by the service literature of 4 different manufacturers.
| Cause |
|---|
| Wiring, connector or harness of the flow switch damaged or loose |
| Flue or air intake blocked or restricted |
| The flow switch has failed — short circuit or open circuit |
| Heat exchanger fouled or partially blocked |
| System water pressure too low, or a leak somewhere in the system |
| Too many reset attempts: the boiler has locked itself out |
Safety Warning
141 involves electrical or pressure-related components. Do not attempt repairs without proper qualifications. Ensure the boiler is electrically isolated before any inspection. If you notice water leaks, unusual sounds, or pressure anomalies, contact a qualified heating engineer immediately.
Parts & Prices
Prices shown are indicative. Actual prices and availability vary by region.
Step-by-Step Diagnosis
1. Note the exact error code and check the manufacturer's installation and service manual for specific guidance. 2. Check all visible wiring connections for security and condition. 3. Power cycle the boiler — switch off at the mains for 30 seconds, then switch back on. 4. If the fault recurs, check the fault history for related or recurring codes. 5. Inspect the boiler for any obvious signs of damage, leaks, or unusual sounds
How to Fix It
Unplug and re-seat the connector of the flow switch, then check the harness for chafing, corroded pins and breaks in continuity.
Inspect the flue and air intake along their whole length, including the outside terminal, and clear any obstruction or debris.
Measure the resistance of the flow switch with a multimeter and compare it against the manufacturer’s resistance-versus-temperature table; replace it if it is open circuit, short circuit or out of range.
Have the heat exchanger inspected and cleaned; if it is blocked by limescale or sludge the system needs a chemical flush and an inhibitor dose.
Repressurise the system to the pressure stated on the boiler — typically 1.0–1.5 bar (15–22 psi) when cold. If it drops again, look for a leak on pipework, radiator valves and the pressure relief discharge.
Stop resetting: the underlying fault is still present. Switch the boiler off and on to restore the reset attempts, then have the original fault diagnosed.
Refer to the Atag service documentation for the detailed procedure. Only a qualified engineer should carry out these repairs.
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Affected Models
Atag models that can display fault code 141:
| Model Family | Output Range | Frequency |
|---|---|---|
| All Atag models | — | Possible |
Frequently Asked Questions
Unplug and re-seat the connector of the flow switch, then check the harness for chafing, corroded pins and breaks in continuity. According to the technical documentation, this is the first check on the list for 141.
141 is not classified as a high-severity fault, so the boiler can be reset once. If 141 comes back, stop resetting: the underlying cause is still there and needs a qualified heating engineer.