Common problems guide

The most common Vokera Compact A problems

The faults most likely to send a Vokera Compact A into lockout — with plain-English causes, what to check first, estimated repair costs and whether you need a Gas Safe engineer.

21 documented codes
6 most common
6 DIY-safe checks
0 engineer needed

The 6 most common faults

01
RED LED On every 0.5-secs High DIY-safe

Your boiler has encountered a permanent safety lockout and has stopped working to protect itself.

Why it happens: This fault occurs when the boiler's internal safety sensors detect a critical issue that prevents safe operation, such as the system losing water pressure or the burner failing to light correctly. It acts as a final safety barrier, often triggered by a failing temperature sensor or a hardware component like the fan or ignition system reaching the end of its life.

What to try first

Check if the water pressure gauge is between 1 and 1.5 barRotate the mode selector switch to 'OFF/RESET' for 5 secondsSwitch the dial back to the previous setting to see if the boiler restarts

Est. cost
£90-320
Parts
Primary NTC Thermistor, Ignition Electrode, Fan
Full guide for RED LED On every 0.5-secs
02
RED LED Solid High DIY-safe

Your boiler has likely overheated, causing a safety switch to trip and shut down the system to prevent damage.

Why it happens: This fault occurs when the water inside the boiler exceeds a safe temperature, triggering a mechanical safety switch to cut off the burner. The most common reasons are a failed pump that isn't moving water efficiently, or a build-up of sludge and debris that is restricting flow through the heat exchanger.

What to try first

Check that your radiator valves are open to allow water to flow.Ensure the system pressure is between 1 and 1.5 bar on the pressure gauge.Wait for the boiler to cool down, then turn the mode selector switch to 'OFF/RESET' for a few seconds before switching it back to 'ON'.

Est. cost
£90-180
Parts
Overheat Limit Thermostat, Circulation Pump, Thermistor (NTC Sensor)
Full guide for RED LED Solid
03
GREEN LED On every 0.5-secs High DIY-safe

Your boiler has paused because it has detected a temporary issue, likely due to low water pressure or an intake problem, and is waiting for the condition to clear.

Why it happens: This fault occurs when the boiler's safety sensors detect an unstable condition, such as the internal water pressure dropping too low or the air flow being restricted. The system enters a temporary pause to prevent damage, waiting for the correct pressure or air balance to be restored before it attempts to fire up again.

What to try first

Check the pressure gauge on the front of the boiler; it should be between 1 and 1.5 bar.If the pressure is too low, use the filling loop valves to top up the system.Ensure the external flue terminal is not blocked by leaves, debris, or snow.Turn the mode selector switch to 'OFF/RESET' for a few seconds and then back to 'ON'.

Est. cost
£0-180
Parts
Air Pressure Switch, Filling Loop, Fan
Full guide for GREEN LED On every 0.5-secs
04
A04 High DIY-safe

Your boiler has stopped working because the water pressure inside the heating system has dropped too low.

What to try first

Locate the filling loop (a flexible metal hose) underneath your boiler or near your airing cupboard.Open the valves on the filling loop slowly to let water into the system.Watch the pressure gauge on the front of the boiler until the needle reaches the green zone (usually between 1 and 1.5 bar).Close both valves tightly to stop the flow of water.

Est. cost
£80-150
Parts
Pressure relief valve, Expansion vessel, Filling loop
Full guide for A04
05
Green LED On, Red LED Off High DIY-safe

Your boiler has stopped working because the water pressure inside the heating system has dropped too low.

What to try first

Locate the filling loop, which is usually a flexible silver hose under the boiler connecting two pipes.Open the valves on both ends of the loop slowly until you hear water entering the system.Watch the pressure gauge on the front of the boiler and close the valves once the needle reaches 1.5 bar.

Est. cost
£80-120
Parts
Filling loop, Pressure relief valve, Pressure gauge
Full guide for Green LED On, Red LED Off
06
Green LED Off, Red LED Off High DIY-safe

Your boiler is completely unresponsive and failing to receive any electrical current, meaning it cannot operate your heating or hot water at all.

What to try first

Check your home's consumer unit to ensure the circuit breaker or RCD dedicated to the boiler has not tripped.Inspect the fused spur switch located near the boiler to confirm the fuse inside has not blown.Verify that the plug connected to the boiler, if applicable, is pushed firmly into the socket and that the socket is switched on.

Est. cost
£100-250
Parts
External fuse, PCB (Printed Circuit Board), Transformer
Full guide for Green LED Off, Red LED Off

on the Vokera Compact A

Primary NTC ThermistorIgnition ElectrodeFanPrinted Circuit Board (PCB)Overheat Limit ThermostatCirculation Pump

Based on parts cited in our fault code database. Your engineer will confirm what's actually needed after diagnosis.

Call a Gas Safe engineer if…

  • You can smell gas or see signs of a leak
  • The Vokera shows an Emergency or High severity code
  • The boiler keeps locking out after repeated resets
  • You've tried the DIY checks and the fault hasn't cleared
  • There's visible water leaking from the boiler
  • The flame is yellow or orange instead of blue

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See the full 21-code list for the Vokera Compact A