Baxi Boiler Radiator Symbol Flashing

What a flashing radiator symbol normally means

The radiator symbol on a Baxi display shows the heating side of the boiler. Baxi user guides, for example the EcoBlue Advance, describe the heating symbol as flashing when there is a heating demand, so a flashing radiator is the boiler telling you the timer or thermostat has asked for heat. A separate flame symbol shows when the burner is actually lit. When the water reaches the temperature the boiler is aiming for, the flame goes out while the pump keeps pushing the remaining heat round the radiators, and the radiator symbol carries on flashing. When the water cools a little, the burner relights and the flame comes back.

This on and off pattern is deliberate. Stopping the burner from relighting straight away, often called anti-cycling, saves gas and wear. So a flashing radiator symbol with the flame coming and going, and warm radiators, is a boiler doing exactly what it should.

On some Baxi models with plus and minus buttons, the radiator symbol also flashes while you are adjusting the heating temperature, and stops a few seconds after you let go.

How to tell normal flashing from a fault

Look at what else is on the screen. Baxi displays use a small set of extra symbols, and they tell you whether you have a problem.

• Radiator flashing, no other symbol, radiators warm: normal. Leave it.
• Radiator flashing with an R symbol and an error number: a lockout that you are allowed to reset.
• Radiator flashing with a spanner symbol: a fault the user cannot reset. It needs an engineer.
• Radiator flashing with the pressure symbol, or a pressure code: the system pressure is too low for the boiler to run.
• Radiator flashing for an hour or more with cold radiators and no code: the boiler is seeing a demand but cannot deliver heat. Keep reading.

Flashing with a code: the ones that matter

Baxi codes differ a little between ranges, so read the exact number. On a Baxi 600 combi, for example, the user guide lists 118 as primary water pressure too low, 133 as an interruption of the gas supply or flame failure, 125 as a circulation fault and 160 as a fan or fan wiring fault. Other Baxi ranges show low pressure as E119. On two-digit displays, E1 followed by two more digits is one three-digit code shown in two halves.

Low pressure is the one you can fix yourself. Baxi recommends about 1.5 bar, its user guides say to top up once the gauge falls below 0.7 bar (1 bar in some start-up checks), and the boiler will not run below 0.5 bar. Top up at the filling loop following our Baxi boiler pressure guide, then reset. For a flame failure code, check that a gas hob lights and, in freezing weather, that the condensate pipe outside is not frozen, then reset the boiler once. Circulation and fan faults point to parts inside the boiler.

If you can smell gas, do not reset the boiler. Get a window open, turn the meter valve off if you can reach it safely, do not use switches, and call the National Gas Emergency Service on 0800 111 999 once you are outside.

Flashing for ages with cold radiators

If the radiator symbol keeps flashing and the radiators never warm up, the boiler is in a heating demand but the heat is not reaching the rooms. Work through these in order.

• Check the pressure gauge. If it has fallen well under 1 bar, top it up to 1 to 1.5 bar before anything else; below 0.5 bar a Baxi will not run at all.
• Feel the pipes under the boiler. If the flow pipe is hot and the radiators cold, water is not circulating. The pump or a closed valve is the likely cause.
• Check the radiator valves are open, and bleed any radiator that is hot at the bottom and cold at the top. Our guide to bleeding radiators covers whether to do it hot or cold.
• On a system boiler with a cylinder, a stuck motorised valve can leave the boiler cycling without the heating zone opening.
• If the heating temperature knob is set very low, the boiler reaches its target almost at once and spends most of its time resting. Turn it up and watch whether the flame symbol appears.

When to stop and get an engineer

A flashing radiator symbol on its own never needs an emergency call. The time to call is when the radiators are cold and none of the checks above help, when a spanner symbol appears, when a resettable code comes back after one reset, or when pressure you have topped up drops again within a day or two. That last pattern means water is leaving the system somewhere, and our guide to a boiler that keeps losing pressure explains where.

Switch the boiler off at the fused spur if you see water under it (as long as no water is on the spur itself), hear banging from the casing, or the pressure gauge climbs close to 3 bar.

What the engineer checks, and typical costs

For a boiler that flashes the radiator symbol but gives no heat, an engineer checks the pump is turning and pushing water, looks at the diverter or motorised valves, measures the flow and return temperatures, and checks the sensors that tell the boiler how hot the water is. Heavy sludge can also make a boiler overheat quickly and rest constantly, which a flush or a magnetic filter clean helps.

Typical market prices including fitting are roughly £250 to £500 for a diverter valve and £200 to £350 for a fan. A temperature sensor is usually a smaller job.

For Baxi boiler repair the call-out is £60 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.