Vokera Boiler Error Codes: Causes & Fixes
Understanding Vokera boiler error codes helps UK homeowners and landlords spot heating problems early and restore warmth without unnecessary stress. The most common ones include A04 for low water pressure, A01 for ignition failure and A03 for fan issues.
These often stem from everyday wear, minor leaks or simple maintenance needs, but we’ll cover every major code in detail below so you know exactly what to do.
Vokera Boiler Error Codes: Quick Overview
Vokera boilers use clear error codes on the display to show exactly what’s wrong. Most are straightforward to understand and many can be resolved with a quick reset or pressure top-up, while others need a professional eye to keep your system safe. Here’s a handy reference table of all the main codes:
| Error Code | What It Means |
| _St | The boiler has automatically stopped for safety reasons |
| _CL | The boiler needs a professional service |
| A01 | Ignition failure – the boiler could not light the flame |
| A02 | Limit thermostat fault – a safety switch has detected overheating |
| A03 | Fan fault – problem with the fan that safely removes exhaust gases |
| A04 | Low system water pressure – not enough pressure in the heating system |
| A06 | Hot water temperature sensor fault |
| A07 | Main flow temperature sensor fault – water is getting too hot |
| A08 | Return temperature sensor fault |
| A09 | Flue temperature sensor fault |
| A11 | False flame detection – the boiler senses a flame when it shouldn’t |
| A77 | Low temperature thermostat fault |
Depending on your exact Vokera model (such as Compact, Unica or Evolve), you may see slight variations like E or AL codes, but the ones above cover the vast majority of UK installations.
Vokera Error Code A01: Ignition Failure
Error code A01 on your Vokera boiler means the unit tried to start but could not detect a proper flame, so it shuts down safely to prevent any risk.
What Causes Error Code A01
Common causes include the gas supply being turned off or low, a faulty ignition electrode or gas valve, debris in the burner, or low gas pressure at the meter.
How to Fix Error Code A01
- Check your gas meter is on and, if it’s a prepay type, has credit.
- Turn the boiler off at the mains for 30 seconds, then switch it back on to reset.
- If the code returns, do not keep resetting – call a Gas Safe registered engineer straight away to inspect the ignition parts safely.
If sudden ignition problems leave you without heat, boiler cover plans provide fast repairs, parts and labour so you’re never hit with surprise bills.
Vokera Error Code A02: Limit Thermostat Fault
Error code A02 on your Vokera boiler signals that the safety limit thermostat has tripped because it has detected excessive heat inside the unit.
What Causes Error Code A02
This usually happens when water flow is restricted, the pump is struggling or there’s a build-up of sludge or air in the system.
How to Fix Error Code A02
- Bleed all your radiators to release trapped air.
- Check the boiler pressure gauge and top up if needed.
- Reset the boiler and monitor it.
- If the fault returns, book a professional boiler service to clean the system and check the pump.
Vokera Error Code A03: Fan Fault
Error code A03 on your Vokera boiler tells you the fan that extracts combustion gases is not working correctly, often due to speed or signal problems.
What Causes Error Code A03
The fan may be worn, have loose wiring, or be affected by moisture from a small leak.
How to Fix Error Code A03
- Turn the boiler off and on to reset.
- Listen for fan noise when it tries to start.
- If the code persists, a Gas Safe engineer must check and replace the fan if necessary.
Vokera Error Code A04: Low System Water Pressure
Error code A04 on your Vokera boiler is one of the most frequent and simply means the water pressure in your central heating system has dropped too low.
What Causes Error Code A04
It is usually caused by a small leak in pipes, radiators or the boiler itself, or natural pressure loss over time.
How to Fix Error Code A04
- Locate the pressure gauge on your boiler – it should read between 1 and 1.5 bar when cold.
- If low, open the filling loop (usually under the boiler) and slowly add water until the gauge reaches 1.3–1.5 bar.
- Close the valves and reset the boiler.
- If pressure keeps dropping, do not keep topping up – have an engineer find and repair the leak.
If you’re dealing with reduced heating efficiency or odd pressure issues from your boiler, a professional service can diagnose and resolve it before it becomes a costly breakdown.
Vokera Error Code A06: Hot Water Temperature Sensor Fault
Error code A06 on your Vokera boiler means the sensor that measures hot water temperature is not sending the right information.
What Causes Error Code A06
Worn sensors, loose wiring or a fault on the control board are the usual suspects.
How to Fix Error Code A06
- Reset the boiler.
- Check hot water taps are working normally.
- If the code stays, a qualified engineer will test and replace the sensor.
Vokera Error Code A07: Main Flow Temperature Sensor Fault
Error code A07 on your Vokera boiler indicates the main flow sensor has detected water temperatures that are too high.
What Causes Error Code A07
Restricted water flow, sludge in the system, a faulty pump or limescale build-up often triggers it.
How to Fix Error Code A07
- Bleed radiators and check pressure.
- Reset the boiler.
- Arrange a professional flush and service if it returns.
Vokera Error Code A08: Return Temperature Sensor Fault
Error code A08 on your Vokera boiler shows the return sensor is reading temperatures incorrectly, often because flow and return pipes are the wrong way around or the sensor has failed.
What Causes Error Code A08
Faulty sensors, installation mix-ups or circulation problems are typical.
How to Fix Error Code A08
- Reset and monitor.
- An engineer will test both sensors and the pump.
Vokera Error Code A09: Flue Temperature Sensor Fault
Error code A09 on your Vokera boiler means the sensor monitoring exhaust gases in the flue is faulty or the flue is blocked.
What Causes Error Code A09
Debris in the flue, a damaged sensor or poor ventilation.
How to Fix Error Code A09
- Visually check the flue outlet for blockages like leaves or snow.
- Reset the boiler.
- Have a Gas Safe engineer inspect the flue and sensor.
Vokera Error Code A11: False Flame Detection
Error code A11 on your Vokera boiler signals the unit is detecting a flame when there should be none.
What Causes Error Code A11
A sticking gas valve or faulty flame sensor is the main reason.
How to Fix Error Code A11
- Reset once.
- If it returns immediately, turn off the gas supply at the meter and call an engineer without delay.
Vokera Error Code A77: Low Temperature Thermostat Fault
Error code A77 on your Vokera boiler points to an issue with the low-temperature safety thermostat.
What Causes Error Code A77
Similar to A02, but triggered by unusually low temperatures or a faulty switch.
How to Fix Error Code A77
- Check room thermostats and reset the boiler.
- A service visit will confirm and replace the part if needed.
Getting your boiler serviced regularly catches these sensor and fan issues early, keeping repair costs down and your system running efficiently year after year.
How Can You Protect Your Vokera Boiler from Future Error Codes?
At PlusHeat, we make it simple to keep your boiler safe, efficient and reliable. If you’re due for a routine check-up, tune-up or want to prevent future issues, start with our flexible boiler service plans.
If you’re looking for full protection against unexpected breakdowns, emergency repairs and peace of mind all year, our boiler cover plans have you covered.
Frequently Asked Questions
What should I do if my Vokera boiler shows an error code not listed here?
Check your model’s user manual or contact Plus Heat – newer Evolve models use E-series codes that follow similar patterns, and a quick call to a Gas Safe engineer will identify it exactly.
Can cold weather make Vokera boiler error codes appear more often?
Yes, frozen condensate pipes or increased demand can trigger pressure or fan faults. Insulate external pipes and keep the boiler topped up to avoid winter surprises.
How do I know if a Vokera error code needs an emergency call-out?
Any code involving gas, flame or repeated lockouts (A01, A11) should be treated as urgent. For simple pressure drops that you can top up yourself, it’s less critical but still worth monitoring.
Are Vokera boiler error codes covered under landlord responsibilities?
Yes – landlords must ensure boilers are safe and serviced annually. A boiler cover plan takes the stress out of tenant-reported faults and unexpected repair bills.
What’s the typical cost range to fix common Vokera boiler error codes?
Simple resets or pressure top-ups cost nothing, while sensor replacements start around £100–£150 and fan or gas valve work can reach £250–£350. A service plan often reduces these costs dramatically.
