BoilerFaultCodes P blinking
Your boiler is simply performing a standard procedure to keep a small amount of water warm, allowing it to provide hot water to your taps more quickly.
Vokera Unica Fault codes & diagnostics
19 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
Gas 2013-present
The Unica range comes in 5 types
Pick the one you have. The fault codes, GC numbers and manual differ by type.
Each model has its own manual
This boiler uses LED flash patterns
Count the flashes in one repeating group before the pause. That number is your fault code. Do not reset until you have noted it. How to read fault codes →
Severity at a glance
Each cell = one fault code. Hover to identify. 9 High
2 Medium
8 Low
Just want the most common Vokera Unica faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes
All 19 documented codes
Tap any card for details
LED / flash-pattern codes
Digital codes
_CL Your boiler is reminding you that a routine service is due or your landlord needs to be contacted.
Your boiler is reminding you that a routine service is due or your landlord needs to be contacted.
_St
Your boiler has reached a pre-set limit or rental lock set by your landlord and needs them to reset or service it.
(cid:31) Your boiler is currently running its automatic air purge cycle to clear trapped air from the system, which is a normal operational phase.
Your boiler is currently running its automatic air purge cycle to clear trapped air from the system, which is a normal operational phase.
What to check first
- Wait a few minutes for the purge cycle to complete automatically.
- Do not switch off the power unless the code persists for an unusually long time.
A01 Your boiler has failed to light because it is not detecting a flame, which means your heating and hot water have temporarily stopped working.
Your boiler has failed to light because it is not detecting a flame, which means your heating and hot water have temporarily stopped working.
What to check first
- Check that your gas supply is turned on and other gas appliances in the house are working.
- Check if your gas prepayment meter has run out of credit if applicable.
- Locate the boiler's reset button, hold it down for about 5 seconds, and release to see if the boiler reignites.
Parts commonly replaced
- Ignition electrode
- Gas valve
- Printed circuit board (PCB)
Related codes
A02 Your boiler has shut down because it has gotten too hot, likely due to low water pressure in the system.
Your boiler has shut down because it has gotten too hot, likely due to low water pressure in the system.
What to check first
- Check your boiler's pressure gauge to ensure it is between 1 and 1.5 bars.
- Use the filling loop to top up the water pressure if it is too low.
- Press the reset button on your boiler once the pressure is corrected.
Parts commonly replaced
- Limit thermostat
- Pressure switch
- Circulating pump
Related codes
A03 Your boiler has detected an issue with the internal fan that safely removes combustion gases, so it has locked out to prevent unsafe operation.
Your boiler has detected an issue with the internal fan that safely removes combustion gases, so it has locked out to prevent unsafe operation.
Parts commonly replaced
- Fan assembly
- Printed Circuit Board (PCB)
Related codes
A04 Your boiler has stopped working because the water pressure inside the system has dropped too low.
Your boiler has stopped working because the water pressure inside the system has dropped too low.
What to check first
- Locate the filling loop valves underneath your boiler.
- Open the valves slowly to allow water into the system until the pressure gauge reads between 1.0 and 1.5 bar.
- Close the valves tightly and press the reset button on your boiler.
Parts commonly replaced
- Filling loop
- Pressure relief valve
- Pressure sensor
Related codes
A06 Your boiler is struggling to accurately measure the temperature of your hot water, which usually means it will temporarily stop providing hot taps or showers.
Your boiler is struggling to accurately measure the temperature of your hot water, which usually means it will temporarily stop providing hot taps or showers.
Parts commonly replaced
- DHW NTC Thermistor
- Domestic Hot Water Sensor
Related codes
A07 Your boiler has temporarily stopped working because it is getting incorrect temperature readings from its internal sensors, meaning it cannot safely regulate the heat.
Your boiler has temporarily stopped working because it is getting incorrect temperature readings from its internal sensors, meaning it cannot safely regulate the heat.
Parts commonly replaced
- Flow thermistor
- NTC sensor
- Wiring harness
Related codes
A08 Your boiler has temporarily stopped working because it cannot accurately read the temperature of the water returning from your radiators.
Your boiler has temporarily stopped working because it cannot accurately read the temperature of the water returning from your radiators.
Parts commonly replaced
- Return thermistor
- NTC sensor
Related codes
A09 Your boiler has detected that the temperature inside the exhaust flue is too high, or that a safety sensor has failed, and has safely shut down to prevent damage.
Your boiler has detected that the temperature inside the exhaust flue is too high, or that a safety sensor has failed, and has safely shut down to prevent damage.
Parts commonly replaced
- Flue thermistor
- Flue temperature sensor
Related codes
A11 Your boiler has temporarily sensed a flame when it shouldn't be there, so it has locked out to keep you safe.
Your boiler has temporarily sensed a flame when it shouldn't be there, so it has locked out to keep you safe.
Parts commonly replaced
- Flame electrode
- Printed Circuit Board (PCB)
Related codes
A77 Your boiler has detected an issue with its low temperature safety thermostat and needs to be reset, though you will need an engineer if the error keeps coming back.
Your boiler has detected an issue with its low temperature safety thermostat and needs to be reset, though you will need an engineer if the error keeps coming back.
What to check first
- Locate the reset button on your Vokera Unica boiler control panel.
- Press and hold the reset button for a few seconds to clear the fault.
- Wait to see if the boiler fires up normally; if the code returns, do not attempt further fixes.
Parts commonly replaced
- Low temperature thermostat
- Wiring harness
- Printed Circuit Board (PCB)
Related codes
ACO Your boiler has reached its programmed time limit and is simply reminding you that a routine safety service is now due.
Your boiler has reached its programmed time limit and is simply reminding you that a routine safety service is now due.
Adj
Your boiler is currently recalibrating its internal settings to ensure it operates efficiently after a recent change or power cycle.
AUTOSTOP
Your boiler has stopped operating because a pre-set rental agreement timer has expired, meaning you need to contact your landlord or property manager to reset it.
Hours Your boiler is perfectly healthy and is simply resting until you turn on a tap or adjust your heating.
Your boiler is perfectly healthy and is simply resting until you turn on a tap or adjust your heating.
What to check first
- No action required
- This is the normal state when the boiler is waiting for a demand for hot water or heating
P
Your boiler is simply performing its normal routine of keeping water warm inside so you get hot water faster when you turn the tap on.
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