Boiler fault codes
Vokera Boiler Fault Codes Explained
Vokera boilers use two main code families. Unica, Vision and similar models show A codes such as A01 for ignition failure and A04 for low water pressure. Evolve models show E codes such as E010 for flame lockout. Find your code below, note it before any reset, and reset only once or twice before calling.
Vokera A codes (Unica and similar models)
These are the codes in the Vokera Unica installation and user manual, with Vokera’s own advice. Most tell you to reset once and call an engineer if the fault persists.
- A01: ignition failure, flame not sensed. Check gas reaches the property, then reset. See boiler ignition lockout for the checks.
- A02: limit thermostat fault, meaning the boiler overheated. Vokera’s first check is the water pressure.
- A03: fan tacho signal fault. The fan is not reporting its speed. Reset once; a repeat needs an engineer.
- A04: insufficient system water pressure. Top up to 1 to 1.5 bar with the boiler cold, then reset. If it drops again, read why boiler pressure falls to zero.
- A06, A07, A08: hot water, flow and return thermistor faults, including over-temperature on flow and return.
- A09: flue thermistor fault or flue over-temperature.
- A11: false flame, a temporary fault where a flame is sensed when there should not be one.
- A77: low temperature thermostat fault. Reset once; a repeat needs an engineer.
- _CL means a service is due, and P or a blinking P means preheating is active. Neither is a fault.
Vokera E codes (Evolve models)
The Evolve manual uses a three-digit E code and marks each alarm as temporary, which clears on its own, or final, which needs a reset.
- E010: flame lockout, the Evolve equivalent of A01. Final.
- E011: extraneous flame. Temporary.
- E020: limit thermostat, meaning overheating. Final.
- E030: fan fault. Final.
- E040 and E041: check system water pressure. Vokera says E041 appears when pressure drops below 0.3 bar and gives you about ten minutes to refill before it locks out.
- E042: water pressure sensor fault. Final.
- E060: hot water probe fault on Evolve combis, or a configuration fault on Evolve system boilers. E070 and E080: flow and return sensor faults or over-temperature.
- E090 and E091: flue sensor over-temperature, and a reminder to clean the primary heat exchanger.
How to reset a Vokera boiler
On dial models such as the Unica, Vokera’s manual says to wait two minutes, then turn the mode selector to the OFF/RESET position and back to your usual setting. On the Evolve, reset from the fault screen on the controller. Vokera allows up to three resets there, after which the power has to be switched off to allow more. If you need three, something is wrong.
Low pressure is the fault you can most often clear yourself. If the filling loop does not work, or the pressure drops again within days, there is a leak or a failing expansion vessel. In freezing weather, a frozen condensate pipe outside causes ignition lockouts, and warm, not boiling, water thaws it.
When a Vokera code means calling an engineer
Fan, thermistor, flue and repeat ignition codes all mean a part inside the casing. Leave the case closed. Gas work is carried out by Gas Safe registered engineers. If you smell gas, open windows, turn off at the meter if it is safe to, use no switches, get outside and call the National Gas Emergency line on 0800 111 999, as covered in what to do if you smell gas.
For anything else, our boiler repairs visits start with the £60 call-out, and the repair price is agreed on site before any work starts. If you have no heating tonight, see emergency boiler repair. Other brands are listed on the boiler fault codes index.
| Code | What it means | Can you clear it yourself? |
|---|---|---|
| A01 | Ignition failure: flame not sensed (Unica, Vision) | Yes, once; call if it returns |
| A02 | Overheat: limit thermostat has tripped (Unica, Vision) | Yes, once; call if it returns |
| A03 | Fan speed signal fault (Unica, Vision) | Yes, once; call if it returns |
| A04 | Not enough water pressure in the system (Unica, Vision) | Yes, once; call if it returns |
| A06 | Hot water temperature sensor fault (Unica, Vision) | Yes, once; call if it returns |
| A07 | Flow temperature sensor fault or overheat (Unica, Vision) | Yes, once; call if it returns |
| A08 | Return temperature sensor fault or overheat (Unica, Vision) | Yes, once; call if it returns |
| A09 | Flue temperature sensor overheat or fault (Unica, Vision) | Yes, once; call if it returns |
| A77 | Low temperature thermostat fault (Unica, Vision) | Yes, once; call if it returns |
| E010 | Flame lockout (Evolve) | Yes, once; call if it returns |
| E020 | Overheat: limit thermostat has tripped (Evolve) | Yes, once; call if it returns |
| E030 | Fan fault (Evolve) | Yes, once; call if it returns |
| E041 | Water pressure below 0.3 bar; refill within ten minutes (Evolve) | Yes, once; call if it returns |
| E042 | Water pressure sensor fault (Evolve) | Yes, once; call if it returns |
| E091 | Primary heat exchanger needs cleaning (Evolve) | No, call an engineer |
Questions people ask
How many times can I reset a Vokera boiler?
Once or twice. The Evolve allows three resets from the controller before the power has to be switched off. If the same code returns, note it and call an engineer rather than resetting again.
What pressure should a Vokera boiler be at?
Vokera’s Unica manual says the gauge should read between 1 and 1.5 bar with the boiler off and cooled to room temperature.