Worcester Boiler Flashing Blue Light: What It Means

Steady blue, flashing blue: what the light is telling you

On most Greenstar boilers the blue light is the mains indicator. Lit and steady, it tells you the boiler has electricity and is ready to run. When it starts flashing, the boiler has stopped itself because something went wrong, and it will not fire again until the fault clears and someone resets it. Worcester calls this a lockout. It is a safety feature, not a sign the boiler is about to fail dangerously.

Look at the display before you touch anything. Models with a screen, such as the Greenstar i, Si, Ri and the newer 4000 and 8000 Life ranges, show a code alongside the flashing light. Write the code down, including any number that appears after it, because that is what tells an engineer where to start. On older models without a text display there may be no code to read, so note how the light flashes, whether any other light is lit, and what the boiler was doing when it stopped. The fault table in the user manual matches those patterns to a cause.

The faults that usually cause it

Almost every flashing blue light comes back to one of a short list of problems. They are listed roughly from the most common to the least, which is also a sensible order to check them in.

• No flame after ignition: the boiler sparked but never sensed a flame. On screen this is usually EA 227. Causes include no gas reaching the boiler, a frozen or blocked condensate pipe, a worn ignition electrode or a faulty gas valve.
• Low water pressure: well below 1 bar most Greenstar boilers stop and show a pressure code, commonly CE 207 on recent models. The gauge on the front will read low, often near zero.
• Overheating: the overheat safety device has tripped, shown as E9 with a cause code. A seized pump, a closed valve or heavy sludge are the usual reasons.
• Fan faults: the fan is running too fast or too slow, shown as C6, usually followed by 215 or 216.

Checks you can do safely before resetting

Everything below is outside the boiler casing. Nothing here needs tools beyond a kettle of warm water.

• Turn on a gas hob or gas fire. If it will not light, the problem is the gas supply, not the boiler. On a prepayment meter, check the credit and the emergency credit.
• Read the pressure gauge. With the heating cold it should sit between 1 and 1.5 bar. If it is lower, top it up at the filling loop or follow our guide to low pressure on a Worcester boiler.
• In frosty weather, find the white plastic condensate pipe where it leaves the house. If it is frozen, pour warm water, not boiling, along its length until it runs clear.
• Check the timer and room thermostat are calling for heat, so the boiler has a reason to fire after the reset.

If you can smell gas, do not reset anything. Open windows, shut the gas off at the meter if you can safely reach it, avoid switches, then leave and call the National Gas Emergency Service on 0800 111 999.

How to reset a Worcester boiler that is flashing blue

The method depends on the control panel. On models with a reset button, press and hold it for about five seconds, which is what Worcester’s user instructions ask for. On dial models like the Greenstar Ri, turn the central heating knob to the reset mark on the dial, hold it there for about five seconds, then turn it back to your usual setting. The blue light stops flashing once the reset has taken. Check the manual for your model if you cannot find either.

If the reset works, the blue light goes back to steady and the boiler tries to fire when the heating or hot water asks for it. Give it a few minutes and run a hot tap to test it.

Reset once, or twice at most after fixing something like the pressure or a frozen pipe. Each extra reset on an ignition fault is another failed start for the electrode and gas valve, and it hides the pattern an engineer needs to see. If the light starts flashing again, the boiler has told you the fault is real. Our wider guide to ignition lockout explains why the second lockout matters more than the first.

When a flashing blue light cannot wait

A lockout is not an emergency in itself, but no heating and no hot water can be. Get help the same day if there are young children, older or unwell people in the house, if it is freezing outside, or if the boiler is locking out with an overheat or fan code rather than a pressure or gas-supply problem you can fix.

Stop and switch the boiler off at the fused spur if you see water dripping from under the casing and the spur itself is dry, hear loud banging before it locks out, or notice sooty or scorch marks on the casing or around the flue. Those point to faults that should not be reset at all.

What the engineer checks, and what it tends to cost

An engineer starts with the fault history stored in the boiler, then tests the gas pressure at the inlet, the flue and air path, the condensate route and the flame sensing. For a no-flame lockout the usual repairs are cleaning or replacing the ignition electrode, clearing a blocked condensate trap or siphon, or replacing the gas valve. Overheat faults are traced to the pump, a diverter valve or a partly blocked heat exchanger.

As a guide to typical market prices, including fitting, an ignition electrode is usually around £80 to £160, a fan around £200 to £350 and a main circuit board around £350 to £700. The price depends on the model and on whether the part is in stock.

For a Worcester boiler repair there is a £60 call-out at any hour, and the repair price is agreed with you on site before any work starts. Gas work is carried out by Gas Safe registered engineers.