Flame rollout switch open: a serious condition (flame escaping the burner area); shut down and call a pro
The 6-FLASH error code on Daikin boilers indicates flame rollout switch open: a serious condition (flame escaping the burner area); shut down and call a pro.
Daikin 6-FLASH means: flame rollout switch open: a serious condition (flame escaping the burner area); shut down and call a pro. On this component the documented failure modes are no gas reaching the burner, or the gas supply is shut off, flue or air intake blocked or restricted or ignition or detection electrode dirty, worn or out of position. A Gas Safe registered engineer should diagnose the root cause.
What Does 6-FLASH Mean
The 6-FLASH code is shown by the boiler’s control board when it detects flame rollout switch open: a serious condition (flame escaping the burner area); shut down and call a pro. 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 6-FLASH 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 6 different manufacturers.
| Cause |
|---|
| No gas reaching the burner, or the gas supply is shut off |
| Flue or air intake blocked or restricted |
| Ignition or detection electrode dirty, worn or out of position |
| Faulty gas valve, or its wiring and connector |
| Control board (PCB) faulty |
Safety Warning
6-FLASH 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 furnace cabinet or work on the gas valve, burner, igniter or venting yourself. Repeated resets are unsafe. Have it diagnosed and repaired by a licensed HVAC technician.
Parts & Prices
Prices shown are indicative. Actual prices and availability vary by region.
Step-by-Step Diagnosis
Note the exact error code and check the manufacturer's installation and service manual for specific guidance
Check all visible wiring connections for security and condition
Power cycle the boiler — switch off at the mains for 30 seconds, then switch back on
If the fault recurs, check the fault history for related or recurring codes
Inspect the boiler for any obvious signs of damage, leaks, or unusual sounds
How to Fix It
Reset the boiler after investigation
repair any loose connections or damaged wiring
replace the faulty component identified during diagnosis
if the fault persists after basic checks, contact a qualified heating engineer with the exact error code
Check that the gas service valve is open and that other gas appliances in the property work. If they do not, the problem is the gas supply, not the boiler.
Inspect the flue and air intake along their whole length, including the outside terminal, and clear any obstruction or debris.
Refer to the Daikin service documentation for the detailed procedure. Only a qualified engineer should carry out these repairs.
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Affected Models
Daikin models that can display fault code 6-FLASH:
| Model Family | Output Range | Frequency |
|---|---|---|
| All Daikin models | — | Possible |
Frequently Asked Questions
Reset the boiler after investigation. According to the technical documentation, this is the first check on the list for 6-FLASH.
6-FLASH 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.