Cable loom (connects gas valve) might have short circuited, gas valve assembly defective or electronic control system issue
The F61 error code on Vaillant boilers indicates cable loom (connects gas valve) might have short circuited, gas valve assembly defective or electronic control system issue.
Vaillant F61 means: cable loom (connects gas valve) might have short circuited, gas valve assembly defective or electronic control system issue. The usual causes are gas valve coil failure (electrical fault), gas valve stuck closed or partially open or gas supply interrupted (prepayment meter, emergency control valve). A Gas Safe registered engineer should diagnose the root cause.
What Does F61 Mean
The F61 code is shown by the boiler’s control board when it detects cable loom (connects gas valve) might have short circuited, gas valve assembly defective or electronic control system issue. 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 F61 and the boiler stops until the fault is cleared |
Common Causes
Causes documented in 18 technical sources.
| Cause |
|---|
| Gas valve coil failure (electrical fault) |
| gas valve stuck closed or partially open |
| gas supply interrupted (prepayment meter, emergency control valve) |
| incorrect gas pressure (too high or too low) |
| gas valve wiring fault |
| PCB not sending open signal to the gas valve |
Safety Warning
F61 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. Gas-related fault. Do not open the boiler casing or attempt repairs to the gas valve, burner, ignition or flue. Repeated resets are unsafe. Diagnosis and repair must be carried out by a Gas Safe registered engineer.
Parts & Prices
Prices shown are indicative. Actual prices and availability vary by region.
Step-by-Step Diagnosis
after gas valve turns off Check gas valve
burner tubes and injectors or electronics defect F
How to Fix It
Restore the gas supply if interrupted
replace the gas valve if it is stuck or electrically faulty — Gas Safe registered engineer only
adjust gas pressure if out of specification
repair wiring between gas valve and PCB
if PCB is not sending signal, replace the PCB. Warning: never attempt gas work unless you are Gas Safe registered
Refer to the Vaillant service documentation for the detailed procedure. Only a qualified engineer should carry out these repairs.
Diagnostic Tools
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Affected Models
Vaillant models that can display fault code F61:
| Model Family | Output Range | Frequency |
|---|---|---|
| All Vaillant models | — | Possible |
Frequently Asked Questions
Restore the gas supply if interrupted. According to the technical documentation, this is the first check on the list for F61.
F61 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.