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Baxi displays the code in two parts. Wait for the whole thing before you read it, because E119 and E133 both start with E1.
No heating or hot water right now? Call 0203 868 6134. We will tell you the earliest realistic slot rather than the one you want to hear.
Two details to start. Add the fault code and your postcode and we can usually tell you the likely part before we attend.
Three steps, no sales pitch, and you will know where you stand before an engineer is booked.
Half the Baxi codes people call us about are not boiler faults. E119 is the water in your system, E168 is often the electricity supply, and E110 is usually the pump or trapped air rather than the boiler cooking itself. Knowing which side of that line you are on decides whether this costs you anything at all, and we will tell you on the phone rather than on the doorstep.
Baxi have built more boilers in Britain than almost anyone, so the failure pattern is well mapped. Six parts cover most of it.
A Baxi shows its fault in two parts. E1 appears first, then the digits that complete it. People read the first half, look it up and get an answer for a different fault, because E119 and E133 and E110 all begin identically and have nothing else in common.
What the boiler is saying: the pressure in the sealed system has dropped under roughly 0.5 bar, which is not enough to fire safely, so it stopped.
What you can safely do: find the filling loop, usually a braided silver hose with one or two small valves under the boiler, and open it until the gauge reads between 1 and 1.5 bar cold. Close it fully. Reset once. This is the one Baxi code most householders can clear themselves.
The part that gets blamed wrongly: a boiler fault at all. The boiler is reporting the state of your pipework.
The exception worth knowing: if the gauge reads a healthy 1.2 bar and the boiler still says E119, the pressure sensor has failed rather than the pressure. That is a part, and a small one.
What does the gauge read? That single number tells us which of these it is.
The boiler asked for gas, tried to ignite, saw no flame and shut the valve. It is the second most common Baxi code and it has three usual causes in a fixed order of likelihood.
First, the gas itself. Does the hob light? Has a meter been changed, or a prepayment credit run out? An E133 with no gas anywhere in the house is not a boiler problem.
Second, in cold weather, the condensate pipe. The white plastic pipe running out through the wall to a drain freezes, the boiler cannot discharge and it stops. Pour warm water along it. Warm, never boiling, which splits it.
Third, the electrodes. Worn, cracked or carboned, so the spark never reaches the burner or the flame is never confirmed.
The part that gets blamed wrongly: the circuit board, which did its job by shutting the gas off rather than continuing to open a valve into a boiler that was not lighting.
Check the hob first. It takes ten seconds and it changes the answer completely.
The water went past the limit the safety thermostat allows and the burner shut down. Baxi record two versions of this and the difference matters.
Exceeded on gradient means the temperature climbed too fast. Exceeded on overtemperature means it simply went too high. The first points more firmly at circulation, the second can also be a sensor reading wrongly.
In practice it is: a jammed pump or air in the circuit. Both produce the same effect, which is heat being made faster than the system carries it away, so it cooks in one place.
The part that gets blamed wrongly: the heat exchanger, and not the safety thermostat either. The thermostat is the part reporting the problem. Replace it and leave the circulation alone and it trips again within days.
What helps most: not a part. Getting the sludge out of the pipework deals with the cause where a component swap usually does not.
Leave it switched off and tell us whether any radiator was cold before this started.
The boiler is firing but the water is not moving through it properly. Close relation of E110, and the two often alternate on the same boiler over a few weeks.
In practice it is: a pump that is running but not shifting anything, a closed or seized valve somewhere on the system, or a heat exchanger silted enough to restrict the flow through it.
The related code: E270 is a dry fire, which means the boiler tried to run with effectively no water in it at all. If you have seen both, deal with it before running the boiler again.
Worth checking yourself: are all the radiator valves actually open? A thermostatic valve that has seized shut over the summer is a genuinely common cause and costs nothing to find.
Which radiators get warm and which stay cold? That map is the diagnosis.
Here is the part almost nobody is told: this code does not appear the first time the flame drops out. The boiler counts, and E128 is recorded after roughly twelve flame failures.
What that means for you: by the time E128 is on the display, the fault has been developing for days or weeks. Anybody who tells you it has just happened has not read the code properly.
In practice it is: the sensing electrode, gas pressure that sags when the boiler is under load, or flue gases finding their way back into the air intake from a damaged or badly sited terminal.
The part that gets blamed wrongly: fixed by resetting. Reset it and the counter starts again, so you get a few more days and then the same code, and the underlying fault is now weeks older than it was.
Has the heating been dropping out briefly before this? That is the same fault, earlier.
The board asked the fan for a speed and did not get it. E161 is the same family.
In practice it is: the fan, and on a Baxi it usually announces itself. If the boiler has been noisier than it used to be for a few weeks, that is this fault earlier in its life.
What is worth checking before the fan is ordered: the wiring and the plug at the fan itself. On this range a connection that has worked loose produces the identical code, and that is a very different bill.
The part that gets blamed wrongly: only the fan. A flue partly blocked by leaves or nesting material makes a healthy fan work against resistance the board reads as a fault.
Has it been noisy lately, or did it stop without warning?
E168 is Baxi's catch-all. It covers a genuine control board lockout, but it also appears while the boiler is restarting after the electricity has been interrupted.
What to do first: reset it once. If the power flickered, if the lights dipped, if a breaker tripped, or if you have had work done on the consumer unit, an E168 that clears on one reset and never comes back was the power cut, not the boiler.
What it usually is if it comes straight back: the control board, and at that point the age of the boiler starts to matter more than the fault does.
The part that gets blamed wrongly: a reason to reset repeatedly. One attempt tells you what you need to know. Four attempts tell you nothing and hide a fault that is still there.
Did the power go off recently? Say so, it changes the likely answer.
Older Baxi models have no digital display. They report through a row of indicator lights, and the fault is the combination rather than a number.
What matters is which lights are on solidly, which are flashing and which are off, read left to right. A fan fault, an overheat lockout, a circulation fault and a board fault are all different combinations of the same three lights.
What to do: note what the front panel shows while the fault is up, or write down the state of each light in order. That description is worth exactly as much as a code, and it saves an engineer working it out from scratch on the doorstep.
One combination is not a fault at all: everything off usually means the boiler has no power, which sends people looking inside the casing when the answer is a tripped breaker or a spur switch somebody knocked.
Describe the lights over the phone and we can usually name it before we set off.
| Code | What the boiler is saying | What it usually turns out to be |
|---|---|---|
| E117 | System pressure too high | A filling loop left open, more often than a fault |
| E118 | System pressure low, on some models | Read it exactly as E119 above |
| E130 / E131 | Flue thermostat tripped | The flue, or the thermostat on it, not the water |
| E134 / E135 | Gas valve open with no gas, or supply interrupted | The supply first, the valve second |
| E154 | Primary flow fault | Circulation again, read alongside E125 |
| E164 | Water pressure sensor fault | The sensor, when the gauge itself reads normal |
| E270 | Dry fire | Stop using it and call somebody |
| E384 | Flame detected with the gas valve shut | Moisture on the electrode, or a valve passing |
| E385 | Incoming voltage too low | Your electricity supply, not the boiler |
A Baxi will stop and record E385 if the incoming mains voltage falls below roughly 195 volts. That is a fault in the electricity arriving at the property rather than anything inside the boiler, and it is a genuine possibility in a flat on a long shared supply or a house with elderly wiring. The boiler takes the blame for something happening outside it, and no amount of replacing parts will make any difference.
Baxi have been building boilers in Britain since the 1860s, and that history creates a set of problems no newer make has.
This is the single most common Baxi call we take that turns out not to be a repair. The boiler loses power, comes back, and either sits showing E168 while it restarts or has quietly lost its clock and programme.
What to try before anybody attends: reset once and wait a full two minutes. Then check the programmer, because a controller that has lost its schedule looks exactly like a boiler that has stopped working.
The related fault: Baxi are notably sensitive to a poor supply, and a boiler that keeps stopping in a property where the lights dim when the shower runs is telling you something about the electrics rather than about itself.
Did anything else in the house lose power at the same time? Call 0203 868 6134.
Baxi Heating also make Potterton and Main. The three brands are not competitors, they are the same group, and they share fault codes and a great many components between them.
Why this is good news: parts availability is far better than a badge on its own would suggest, and an engineer who knows Baxi codes knows Potterton codes without looking them up.
Where it catches people out: a quote for a genuine part can be met with a much cheaper equivalent carrying a different brand name, and both are correct. Ask which group the part comes from rather than which brand is printed on it.
We repair Potterton and Main alongside Baxi for exactly this reason.
Baxi made the Bermuda, a boiler that sits in the chimney breast behind a gas fire rather than hanging on a wall. Plenty are still working in London terraces and nobody under forty recognises what they are looking at.
How to tell: there is no boiler visible anywhere in the house, but there is a gas fire in a chimney breast and a hot water cylinder in a cupboard upstairs. The boiler is behind the fire.
What you need to know: these are heat only boilers feeding a cylinder, so the diagnosis is never just the appliance. Parts for the fire front and for the boiler behind it are different supply chains, and one can be available when the other is not.
Before anybody condemns it: a working back boiler that has been serviced is not automatically a replacement job. When it is, the cost is genuinely higher than a normal swap because the flue and the fireplace both have to be dealt with, and you should hear that at the quoting stage rather than mid-job.
Is your boiler behind a gas fire? Say so when you call. Call 0203 868 6134.
Ask three people what a Megaflo is and you will get two answers, both correct. It is a Baxi system boiler, and it is also one of the best known unvented hot water cylinders in the country.
Why it matters when you call anybody: "my Megaflo has stopped working" could mean a wall hung gas appliance or a large white cylinder in a cupboard, and they are entirely different repairs needing different qualifications.
If yours is on the wall and burns gas, it is the boiler. If it is a tall insulated tank with pipes and valves on the side and no flame anywhere near it, it is the cylinder, and that is unvented cylinder work rather than boiler work.
Not sure which you have? Describe where it is and we will tell you. Call 0203 868 6134.
Half of these are not boiler faults
E119 is the water in your system. E168 is often the electricity supply. E110 is usually a pump or trapped air rather than the boiler cooking itself. Knowing which side of that line you are on decides whether this costs you anything at all.
The label is behind the front panel or on the underside. Baxi have renamed their ranges more often than most, so the name on the front tells you roughly when it was fitted.
Current Baxi naming is a series number, then the type, then the output. A 800 Combi 30 is an 800 series combi rated 30 kilowatts. A 600 System 24 is a 600 series system boiler at 24 kilowatts.
If yours says System or Heat, you have stored hot water somewhere in the house, and the cylinder is as likely to be the fault as the boiler is.
Bermuda is the back boiler, behind a gas fire rather than on a wall. Solo is the long running heat only range and there are plenty still working.
Duo-tec and Platinum are the ranges most commonly on London walls now, usually badged with an output and HE or HE A. EcoBlue, sold as Advance and Plus, followed them.
200, 400, 600 and 800 are the current naming, with 800 at the top. Megaflo appears as a system boiler name as well, which is a source of confusion covered above.
The practical point: anything named Duo-tec or later shares the E code system described on this page. Anything older is likely to be reporting through indicator lights instead.
Baxi have used the same range names across several revisions, and a Duo-tec fitted in one year does not always take the same parts as one fitted three years later. The name on the front is not enough to order by.
The serial number and GC number on the label identify exactly which revision is on your wall. Ordering by range name alone is how the wrong part arrives and a second visit gets booked.
Read us the serial from the label when you ring. It takes a moment and it is the difference between one visit and two. We repair every make of boiler, and this advice is the same for all of them.
London is a hard water city almost everywhere, and that is the single biggest difference between repairing a Baxi here and repairing one in Manchester or Glasgow.
Water here carries roughly 277 milligrams of calcium carbonate per litre, and between districts the figure runs from about 250 to over 350. That comes from chalk in the Chilterns and the North Downs, which both the Thames and the Lea run through. In a combi it produces one predictable result: the plate heat exchanger scales, faster than the intervals printed in the manual allow for.
It is the same story in Hampstead Garden Suburb and Finchley as it is in Sanderstead and Selsdon. The water is hard, the plate heat exchanger scales, and the only question is whether anybody checks it before condemning the boiler.
Hardness is not uniform, and it does not follow borough boundaries. It varies by supply zone and can change over a short distance, so your supplier publishes a figure for your own postcode and it is worth reading before anybody guesses.
Scale drops out of solution faster the hotter the water gets. A combi set to deliver taps at 65 degrees furs up its plate heat exchanger noticeably faster than one set to 50, which is still hot enough to scald. Turning that dial down costs nothing and is the most effective thing a householder in a hard water area can do. This applies to the tap setting, not to a cylinder, which must reach 60 degrees for safety.
Where there is a cylinder there are two appliances, and only one of them is on the wall.
Combi work is all some London firms will do, which leaves the larger houses awkwardly served. A Baxi system or heat only boiler feeds a separate cylinder with its own thermostat, immersion element and, if unvented, its own safety devices. Two appliances, not one, and the half that fails is frequently the half with no display on the front.
The cylinder sensor reports the stored water temperature back to the boiler from a pocket on the tank. Failed, or worked loose, and the cylinder goes cold while the radiators stay hot. Small part, short job, wrong appliance blamed.
The motorised valve decides where the heat goes. When the motor or microswitch fails you lose one side of the system or get both at once, and on most installations only the head has to change.
The immersion element is the backup for when the boiler is down, and hard water eventually kills it. Test before condemning the tank. In the larger houses we attend around Esher, Claygate and Thames Ditton, a scale reducer normally goes in alongside.
An unvented cylinder is a pressure vessel. It carries an expansion vessel, a pressure reducing valve, an expansion relief valve and a temperature and pressure relief valve, all discharging through a tundish. Water running at the tundish means one of them has failed. Do not leave it and never cap it off.
Unvented work is notifiable and needs a G3 qualification on top of Gas Safe registration. Our engineers hold both, so the boiler and the cylinder are dealt with on one visit rather than two appointments and two charges. That is why unvented cylinder repair sits alongside the boiler work instead of being farmed out.
Swapping stored hot water for a combi to free an airing cupboard is the change people most often ask us to reverse. A combi cannot run two showers at once, whatever the output on the box, because it heats water as it passes rather than storing it. In a house with three bathrooms the honest answer is usually to keep the cylinder and spend the money replacing it if it is old, rather than removing it.
We would sooner keep a boiler running than sell you a new one. The age on the label does not settle this. The failed component does.
| What has failed | Under 8 years | 8 to 14 years | 15 years and older |
|---|---|---|---|
| Pressure sensor, flow and return sensors | Repair | Repair | Repair if parts exist |
| Ignition and sensing electrodes | Repair | Repair | Repair if parts exist |
| Expansion vessel, pump | Repair | Repair | Repair |
| Fan, or fan wiring | Repair | Repair | Depends on the rest of the boiler |
| Diverter valve, plate heat exchanger | Repair | Repair | Repair if the part is still made |
| Gas valve | Repair | Depends on the rest of the boiler | Replace |
| Control board | Check the guarantee first | Borderline, we will be straight with you | Replace |
| Main heat exchanger | Guarantee claim if registered | Usually replace | Replace |
Nothing is obsolete at this age, and a failure here is a single part rather than a boiler wearing out. An electrode, sensor, fan or pump on a six year old Duo-tec or 800 is a repair, without qualification.
Check what cover you have before booking anybody, us included. Baxi terms vary by range and by whether the boiler was registered after installation, so it is worth two minutes with the serial number rather than an assumption.
A replacement quote at this age deserves one question: which part, and what does that part cost separately? The gap between those two answers is usually the whole conversation.
Still a clear repair: electrodes, fan, pump, pressure sensor, expansion vessel, diverter valve. These are ordinary wear items and they say nothing about the condition of the rest of the boiler.
The conversation changes with a main heat exchanger, or a second significant failure inside a year. At that point the arithmetic favours replacing the boiler, and the question is not only what has gone today but what goes in the next two winters.
Baxi's advantage at this age is availability. Because Potterton and Main share the same parts, the supply chain is deeper than the badge suggests and fewer repairs stall waiting for something to arrive.
Past this point availability starts to take over from cost. A Solo or an early Duo-tec can be mechanically sound and still unrepairable, because the one part it needs is no longer made, and a repair then is not slow or expensive, it is impossible.
The Bermuda is its own conversation. Replacing a back boiler is a bigger job than swapping a wall hung appliance, because the flue and the fireplace both have to be dealt with, and the figure should reflect that from the first quote rather than appearing halfway through.
We will tell you whether the part still exists before you spend anything on a diagnosis. What actually moves the number is set out in our guide to repair and replacement costs.
Local boiler repair specialists
Clear advice. Careful repairs. Family-friendly service.
Call 0203 868 6134London, north and south of the river. These are the districts we work in most.
These are where we work most, not a boundary. An engineer attends anywhere in north London and south London. Tell us where you are and we will say plainly when we can get to you.
If you smell gas: do not touch any switches. Open the windows, leave the property, then call the National Gas Emergency Service on 0800 111 999. That line is free and open 24 hours. Call them before you call us.
If a carbon monoxide alarm is sounding: get everyone out immediately, then call 999 if anyone feels unwell. Do not go back in until the property has been ventilated and checked.
If the boiler locks out repeatedly: try one reset. If it locks out again straight away, stop. Repeated resets hide a fault that is still there, and on a gas appliance that is not a risk worth taking.
Under the Gas Safety (Installation and Use) Regulations 1998, only a Gas Safe registered engineer may work on gas appliances. Never open the boiler casing yourself.
Usually, yes. E119 means the system water pressure has fallen below roughly 0.5 bar, which is too little to fire safely. Open the filling loop, the braided silver hose under the boiler, until the gauge reads between 1 and 1.5 bar cold, close it fully and reset once. What you cannot fix is why it dropped: once a year is normal, every few weeks means a leak, every few days means the expansion vessel has lost its charge. If the gauge already reads 1.2 bar and E119 is still showing, the pressure sensor has failed rather than the pressure.
Because the display shows the code in two parts. E1 comes up first, then the digits that complete it, and the complete number is the diagnosis. This catches people out constantly, because E119, E133 and E110 all begin the same way and are entirely different faults with entirely different repairs. Wait for the whole thing before you look it up or call anybody, and write it down before you reset, because resetting clears it from the screen.
E133 means the boiler tried to light and failed. Check three things in order. Does anything else in the house run on gas, because a hob that will not light points at the supply rather than the boiler. In cold weather, is the white plastic condensate pipe outside frozen, which you can thaw with warm water, never boiling. Then the electrodes, which wear out and stop making a reliable spark. It is rarely the control board, which shut the gas off precisely because the boiler was not lighting.
E110 means the water went past the temperature limit and the safety thermostat shut the burner down. It is almost always circulation rather than the burner, so a jammed pump, a seized valve or air in the circuit, which leaves the boiler making heat faster than the system carries it away. Replacing the thermostat rarely helps because it is the part reporting the problem rather than causing it. Flushing the sludge out deals with the cause where a component swap usually does not.
It did not appear suddenly. E128 records repeated loss of flame during operation, and the boiler counts them, so the code is written after roughly twelve failures rather than after the first one. By the time you see it the fault has been developing for days or weeks, usually a sensing electrode, sagging gas pressure under load, or flue gases finding their way back into the air intake. Resetting restarts the counter and buys a few days without fixing anything.
The label is behind the front panel or underneath the boiler. Current naming is a series number, then the type, then the output, so an 800 Combi 30 is an 800 series combi at 30 kilowatts. Older ranges read Duo-tec, EcoBlue, Platinum or Solo. Read us the serial when you ring rather than just the name, because Baxi have used the same range names across several revisions and the serial number is what identifies which parts yours takes. We work on every make of boiler.
Age alone does not decide it, the failed part does. Under eight years old, repair it almost without exception. Between eight and fourteen, an electrode, fan, pump or sensor is straightforward while a main heat exchanger changes the arithmetic. Baxi hold an advantage here, because Potterton and Main share components and the parts supply is deeper than the badge suggests. At fifteen, availability decides it. See our boiler replacement page.
A repair cannot be priced until the failed part is known, so treat any firm figure offered before a single question with caution. The figure comes from three things, the part, whether it is in stock on the van, and the labour time. On a Baxi the complete code, both halves of it, usually tells us which part before anybody attends. The rate is agreed beforehand and parts we fit are guaranteed for a year, so nothing is carried out on the assumption that you will approve it afterwards. There is no charge for telling you a repair is not the right call. What actually moves the number is set out in our guide to repair and replacement costs.
Baxi, Potterton and Main are all Baxi Heating, so the fault codes and many of the parts are shared between the three.
No gas supply? Plenty of London flats run without one, and we also cover electric boiler repair.
Half the Baxi codes people call about turn out not to be boiler faults. Read us the complete code, both halves of it, and the model from the label, and we will tell you which side of that line you are on.
Gas Safe registered. Unvented cylinder qualified. Parts guaranteed for a year. Covering London, north and south of the river, 24 hours a day.
