Why your Baxi boiler shows E1
If your Baxi is flashing E1, it is reporting a real fault, but you are only seeing half of the message. The other half appears a moment later, and the two parts together give you the code that matters.
Older Baxi and Potterton boilers have a two-character display. Baxi's installation and servicing instructions for the Duo-tec Combi HE A range (UK Comp No 5122323) state that the codes "are either two or three digit, preceded by the letter E". A three-digit code will not fit on the screen, so the boiler splits it. The same manual gives the worked example that E133 "will be displayed by 'E1' alternating with '33'". None of the Baxi documents we checked lists E1 as a fault in its own right.
Two-digit codes are split in a different place. According to the Duo-tec manual, E50 appears as "E" and then "50". That gives you a quick rule: if the first screen shows E with a single digit beside it, a three-digit code is coming; if it shows E by itself, a two-digit code is coming.
Boilers that display codes this way
| Boiler | Document we checked | What it says |
|---|---|---|
| Baxi Duo-tec Combi 24, 28, 33 and 40 HE A | Installation and Servicing Instructions, UK Comp No 5122323 | E133 shows as E1 alternating with 33 |
| Baxi Megaflo System 15, 18, 24, 28 and 32 HE IE | Installation and Servicing Instructions, UK Comp No 5129838, section 18.2 | Same two and three digit E codes |
| Potterton Promax Combi HE Plus A | User Guide, UK Comp No 5114443, section 5.3 | E133 shows as E1 alternating with 33 |
| Potterton Gold Combi 24, 28 and 33 | User Guide, Baxi Heating UK 2015 | E133 shows as E1 alternating with 33 |
Potterton is part of Baxi Heating UK, which is why the code lists match so closely.
Newer boilers work differently. The Baxi Assure Combi user guide shows codes as plain numbers, such as 133 or 118, next to an R or spanner symbol. The Baxi 200, 400, 600 and 800 Combi 2 ranges use a longer format such as E.04.10, which we cover on our Baxi E04 page. If your display looks like either of those, you are not dealing with a split E1 code.
How to read the full code
- Stand in front of the boiler and watch the display long enough to see it change at least twice.
- Note the two digits that appear after E1, for example 19, 25 or 33.
- Join them up: E1 plus 19 is E119, E1 plus 60 is E160.
- Write down the full code and your boiler's model name, which is shown on the front of the boiler.
- Look up the full code in the table below before you press anything.
Record a ten second video of the display on your phone. It captures both halves of the code, and it is useful to show an engineer or Baxi customer support if the fault comes and goes.
What the full code means
These are the three-digit E1 codes we cover. The meanings follow the wording in Baxi and Potterton fault tables, but not every code appears on every model, so check the table in your own manual too.
| You see | Full code | Meaning | Our guide |
|---|---|---|---|
| E1 then 10 | E110 | Safety thermostat operated (overheat) | Baxi E110, Potterton E110 |
| E1 then 17 | E117 | Primary system water pressure too high | Baxi E117 |
| E1 then 18 | E118 | Primary system water pressure too low | Baxi E118 |
| E1 then 19 | E119 | Water pressure switch not operated (low pressure) | Baxi E119, Potterton E119 |
| E1 then 25 | E125 | Circulation fault (primary circuit) | Baxi E125 |
| E1 then 30 | E130 | Flue NTC operated (overheating in the flue) | See your manual |
| E1 then 33 | E133 | Interruption of gas supply or flame failure | Baxi E133, Potterton E133 |
| E1 then 60 | E160 | Fan or fan wiring fault | Baxi E160 |
| E1 then 68 | E168 | General fault | Baxi E168 |
Safe checks once you know the full code
What you can do depends entirely on the second half of the code.
- E119 or E118 (low pressure): look at the pressure gauge. The Duo-tec manual says E119 appears when primary pressure is below 0.5 bar. Top up to around 1 to 1.5 bar with the heating cold using the filling loop, as our Baxi boiler pressure guide explains.
- E133 (gas or flame): check that your hob or other gas appliances work, that a prepayment meter has credit and that the gas isolation valve under the boiler is open, with its handle in line with the pipe. In a hard frost, thaw a frozen condensate pipe with warm (not boiling) water.
- E110 or E130 (overheat): the Duo-tec and Gold manuals say these can be cleared by turning the selector switch to Reset for at least 5 seconds once the boiler has cooled.
- E117, E125, E160 or E168: there is little a homeowner can safely do beyond a single reset. These point to parts inside the boiler.
On Duo-tec models the Reset position means turning the selector fully anticlockwise against the spring and holding it there for 5 seconds. Stop after 2 or 3 attempts in total.
If you smell gas, do not reset the boiler. Turn the gas off at the meter if it is safe to do so, open windows and doors, avoid using electrical switches and call the National Gas Emergency Service on 0800 111 999.
Typical repair costs in the UK
Costs follow the full code, not the E1 on the screen. These are typical UK ranges for the repairs each code most often leads to.
| Full code | Likely job | Typical cost |
|---|---|---|
| Any | Engineer call-out and diagnosis | Typically £60 to £150 |
| E119 or E118 | Pressure sensor or switch | Typically £100 to £220 |
| E110 or E125 | Pump replacement | Typically £150 to £400 |
| E110 | Overheat or limit thermostat | Typically £100 to £200 |
| E133 | Ignition electrode | Typically £90 to £180 |
| E160 | Fan replacement | Typically £200 to £400 |
When to call a Gas Safe registered engineer
Baxi's manual says that if a reset has no effect, or the codes keep appearing, "further investigation is required". That is the point to book a Gas Safe registered engineer. Do not remove the casing to look for the cause yourself.
When you call, give the full three-digit code rather than "E1", the model name, when the fault appears (first thing in the morning, when you run a tap, when the heating starts) and how many times you have reset it. A clear description often saves a second visit, and if the boiler is still under warranty, contact Baxi before anyone else. Our Baxi fault code hub lists every Baxi code we cover.