ON OFF OFF Fault on heating return NTC probe or return-delivery diff e- rential circuit-breaker
The A07 error code on Nibe boilers indicates on off off fault on heating return ntc probe or return-delivery diff e- rential circuit-breaker.
Nibe A07 means: on off off fault on heating return ntc probe or return-delivery diff e- rential circuit-breaker. On this component the documented failure modes are the return sensor has failed — short circuit or open circuit. A Gas Safe registered engineer should diagnose the root cause.
What Does A07 Mean
The A07 code is shown by the boiler’s control board when it detects on off off fault on heating return ntc probe or return-delivery diff e- rential circuit-breaker. 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 A07 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 |
|---|
| The return sensor has failed — short circuit or open circuit |
Safety Warning
A07 is a gas-related fault. Never attempt to repair or adjust the gas valve, burner assembly, or flue system yourself. All gas work must be carried out by a Gas Safe registered engineer (UK) or licensed HVAC technician (US). Repeated resets after ignition failure can cause unburnt gas to accumulate inside the combustion chamber — this is a serious safety hazard. If you smell gas at any point, turn off the gas supply at the meter, open windows, leave the property, and call your gas emergency service immediately. Warning: this fault code may relate to gas supply, flue or combustion issues. Do not attempt repair — contact a Gas Safe registered 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
Clear any flue blockage
correct the flue installation if it exceeds maximum length or bends
clear ice from the flue terminal (insulate external condensate pipe)
clear the condensate drain
if combustion analysis shows incorrect values, adjust the gas valve or service the burner
Measure the resistance of the return sensor 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.
Refer to the Nibe service documentation for the detailed procedure. Only a qualified engineer should carry out these repairs.
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Affected Models
Nibe models that can display fault code A07:
| Model Family | Output Range | Frequency |
|---|---|---|
| All Nibe models | — | Possible |
Frequently Asked Questions
Clear any flue blockage. According to the technical documentation, this is the first check on the list for A07.
A07 is classified as a high-severity fault: it involves gas, combustion or flue components. Do not keep resetting the boiler and do not attempt the repair yourself — call a Gas Safe registered engineer.