{"id":872,"date":"2026-09-10T05:46:28","date_gmt":"2026-09-10T05:46:28","guid":{"rendered":"https:\/\/www.boilerserviceslondon.co.uk\/blog\/?p=872"},"modified":"2026-09-10T05:46:42","modified_gmt":"2026-09-10T05:46:42","slug":"what-your-boiler-error-code-is-really-telling-you","status":"publish","type":"post","link":"https:\/\/www.boilerserviceslondon.co.uk\/blog\/what-your-boiler-error-code-is-really-telling-you\/","title":{"rendered":"What Your Boiler’s Error Code Is Really Telling You\u00a0"},"content":{"rendered":"\n

If you\u2019ve ever knelt in front of the boiler, torch on your phone, squinting at three letters and a number you\u2019ve never seen before, you\u2019ll know the feeling. Half the time you type it into Google, half the time you just press reset and hope. Fair enough. Nobody grows up learning what \u201cEA 227\u201d means.\u00a0<\/p>\n\n\n\n

Here\u2019s the thing though: that code isn\u2019t the boiler being awkward. It\u2019s the closest thing to plain English a control board can manage, it\u2019s telling you exactly which safety check it failed, at exactly which point in the process. Once you know what it\u2019s checking for, most codes stop being a mystery.\u00a0<\/p>\n\n\n\n

We\u2019re a Gas Safe registered team covering boiler repairs across London<\/a>, and this is the conversation we end up having on the phone almost every day, someone reads out a code, and we can usually tell them in ten seconds whether it\u2019s a two-minute fix or something we need to come out for.\u00a0<\/p>\n\n\n\n

Why boilers even bother with codes<\/strong>\u00a0<\/h2>\n\n\n\n

Every time your boiler fires up, it runs through the same checklist is there enough water pressure, is the pump actually moving that water, can it open the gas valve safely, does it get a flame, and does that flame stay lit the whole time it\u2019s running. If any one of those steps doesn\u2019t go the way it\u2019s supposed to, the boiler stops itself rather than carrying on and hoping for the best. Sensible, really, when you think about what it\u2019s dealing with.\u00a0<\/p>\n\n\n\n

The code on the display is simply pointing at which step tripped it up. That\u2019s also why two completely different problems can throw up codes that look similar, and why the fix for one (topping up the pressure) can be entirely wrong for another that looks almost the same on the screen.\u00a0<\/p>\n\n\n\n

The four things a code is telling you<\/strong>\u00a0<\/h2>\n\n\n\n

Strip away the brand-specific letters and numbers, and nearly every fault falls into one of these:\u00a0<\/p>\n\n\n\n

It\u2019s lost pressure.<\/strong> The boiler isn\u2019t seeing enough water in the system, so it won\u2019t run. This is the one you can normally sort yourself, top up via the filling loop to somewhere around 1.0\u20131.5 bar and see if it holds.\u00a0<\/p>\n\n\n\n

It couldn\u2019t get a flame going.<\/strong> It tried to ignite and gave up after a few attempts. Sometimes that\u2019s your gas supply, sometimes it\u2019s a tired ignition electrode or a gas valve on its way out.\u00a0<\/p>\n\n\n\n

It had a flame, then lost it.<\/strong> Different from the one above, this means it lit fine and then something interrupted it mid-run, a blocked condensate pipe, moisture where it shouldn\u2019t be, or a strong gust down the flue.\u00a0<\/p>\n\n\n\n

It\u2019s overheating or not circulating properly.<\/strong> This one\u2019s mechanical almost every time, a pump that\u2019s seized, a heat exchanger clogged with sludge, or a valve stuck somewhere it shouldn\u2019t be. Don\u2019t keep resetting this one and hoping.\u00a0<\/p>\n\n\n\n

Worcester Bosch codes: EA, E9 and 1017<\/strong>\u00a0<\/h2>\n\n\n\n

If you\u2019ve got a Worcester, you\u2019ll usually see a letter pair with a three-digit number tucked in alongside it.\u00a0<\/p>\n\n\n\n

Code<\/strong>\u00a0<\/td>What\u2019s actually going on<\/strong>\u00a0<\/td>What we\u2019d suggest<\/strong>\u00a0<\/td><\/tr>
1017 (with the little pressure symbol)\u00a0<\/td>Pressure\u2019s dropped too low\u00a0<\/td>Top it up yourself. If it keeps happening, that\u2019s a leak, not a pressure problem\u00a0<\/td><\/tr>
EA 227\u00a0<\/td>Tried to light, couldn\u2019t prove a flame\u00a0<\/td>One reset is fine. Locks out again? Stop resetting, get it looked at\u00a0<\/td><\/tr>
EA 229\u00a0<\/td>Was running fine, then lost the flame\u00a0<\/td>Usually a blocked condensate trap or a flue draught issue\u00a0<\/td><\/tr>
E9\u00a0<\/td>Safety cut-out from overheating\u00a0<\/td>Don\u2019t keep pressing reset, this is nearly always a pump or sludge problem\u00a0<\/td><\/tr>
C6\u00a0<\/td>Fan speed\u2019s out of range\u00a0<\/td>Usually the fan itself or a sensor, needs a part\u00a0<\/td><\/tr>
F0\u00a0<\/td>Something\u2019s wrong internally on the control board\u00a0<\/td>This one needs an engineer\u2019s diagnostic kit\u00a0<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

We\u2019ve written more on this if you\u2019re dealing with an emergency Worcester Bosch fault<\/a> specifically or want to know what a proper Worcester service actually covers<\/a>.\u00a0<\/p>\n\n\n\n

Vaillant codes: F.22 through to F.75<\/strong>\u00a0<\/h2>\n\n\n\n

Vaillant\u2019s ecoTEC range is one we\u2019re out fixing constantly across the older housing stock in Hackney, Islington, and Stoke Newington, hard water in this part of London doesn\u2019t do sensors and heat exchangers any favours.\u00a0<\/p>\n\n\n\n

Code<\/strong>\u00a0<\/td>What\u2019s actually going on<\/strong>\u00a0<\/td>What we\u2019d suggest<\/strong>\u00a0<\/td><\/tr>
F.22\u00a0<\/td>Low pressure, or the system thinks it\u2019s running dry\u00a0<\/td>Repressurise. If it won\u2019t hold, you\u2019ve likely got a leak or a tired expansion vessel\u00a0<\/td><\/tr>
F.27\u00a0<\/td>Detecting a flame when the gas valve\u2019s meant to be shut\u00a0<\/td>This is a safety shutdown, don\u2019t keep resetting it, call someone\u00a0<\/td><\/tr>
F.28\u00a0<\/td>Couldn\u2019t ignite on start-up\u00a0<\/td>Check your other gas appliances first. Still faulting? Book an engineer\u00a0<\/td><\/tr>
F.29\u00a0<\/td>Lost the flame while it was running\u00a0<\/td>Often a supply interruption or an earthing issue at the ignition point\u00a0<\/td><\/tr>
F.75\u00a0<\/td>Pump or pressure sensor not behaving as expected\u00a0<\/td>Usually means one of the two needs replacing\u00a0<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

We covered why hard water areas specifically make Vaillants lose pressure more often in this piece on Vaillant pressure drops<\/a>, worth a read if F.22 keeps coming back.\u00a0<\/p>\n\n\n\n

Baxi codes: E119, E133 and E28<\/strong>\u00a0<\/h2>\n\n\n\n
Code<\/strong>\u00a0<\/td>What\u2019s actually going on<\/strong>\u00a0<\/td>What we\u2019d suggest<\/strong>\u00a0<\/td><\/tr>
E119\u00a0<\/td>Pressure\u2019s dropped below about 0.5 bar\u00a0<\/td>Top up via the filling loop\u00a0<\/td><\/tr>
E133\u00a0<\/td>Gas supply interrupted, or it just couldn\u2019t get a flame\u00a0<\/td>Check the gas hasn\u2019t been cut off anywhere, reset once, call us if it comes back\u00a0<\/td><\/tr>
E28\u00a0<\/td>Flue thermistor fault, sometimes tied to a frozen condensate pipe\u00a0<\/td>Worth checking the condensate pipe for ice first if it\u2019s a cold snap\u00a0<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

Ideal codes: the shorter list<\/strong>\u00a0<\/h2>\n\n\n\n

Ideal keeps things fairly simple. F1 and F2 tend to be pressure or ignition related, while L2 and L5 are lockouts that genuinely need an engineer\u2019s kit to clear properly, not something a reset button sorts out. If you\u2019re weighing up brands for a replacement, our Worcester Bosch vs Baxi vs Ideal comparison<\/a> covers how they stack up day to day.\u00a0<\/p>\n\n\n\n

So, when is it actually okay to just press reset?<\/strong>\u00a0<\/h2>\n\n\n\n

Once, almost always. It costs nothing and tells you whether it was a one-off. It\u2019s what you do after that matters:\u00a0<\/p>\n\n\n\n