BoilerFaultCodesHow to find your boiler fault code
When your boiler stops working, it records a fault code to tell you what went wrong. But different boilers show this in very different ways — a flashing LED, a combination of indicator lights, or a code on a digital screen. This guide explains each method so you can read the right code for your boiler.
Do not press reset yet
The fault code is already showing on your boiler right now. If you press reset, the boiler will attempt to restart and the code will be cleared — you may not be able to retrieve it until the fault recurs. Note the code down first, then search for it, then decide whether to reset.
Jump to your boiler type
Digital display boilers
Most boilers made after 2005 have a small digital or LCD screen on the front panel. When a fault occurs, the boiler locks out and the fault code appears automatically on the screen.
How to read it
Look at the display on the front of your boiler. The fault code is already showing — it does not need to be triggered.
The code is usually 1–5 characters: a letter followed by numbers (e.g. F28, EA, E1) or a number alone (e.g. 133).
Write it down or photograph the display before touching anything.
The code remains on screen until you press the reset button or cut power to the boiler. It will not disappear on its own.
Common digital display brands
Worcester Bosch (Greenstar i/Si/CDi models), Vaillant ecoTEC, Ideal Logic/Vogue, Baxi Platinum/EcoBlue, Potterton Titanium/Promax, Glow-worm Ultimate/Easicom, Viessmann Vitodens, Ferroli, Ariston, Intergas
LED flash pattern boilers
Older boilers — particularly pre-2005 Worcester, Baxi, Potterton, and some Grant models — have no screen. Instead, they use a single LED indicator that flashes in a repeating pattern when a fault occurs. The number and speed of flashes is the fault code.
How to count the flashes
Watch the LED for a full cycle: a group of flashes, a longer pause, then the same group again. The repeating pattern is your code.
Count the number of flashes in one group, before the pause. For example: flash, flash, flash — pause — flash, flash, flash = 3 flashes = fault code 3.
Some boilers use two groups of flashes separated by a short pause. For example: 2 flashes, short pause, 4 flashes, long pause = fault code 24. Check your model's manual.
On some models, the speed matters too: a slow flash (approx. once per second) and a fast flash (four or five times per second) mean different things. Note both the count and the speed.
Write it down exactly as you see it, then look up the pattern in the fault code table for your specific model.
Common LED flash brands
Worcester Bosch (older Ri/CDi/BF models), Baxi (older Duo/Solo/Barcelona), Potterton (Profile/Promax/Suprima), Alpha, Grant
Indicator light combinations
Some boilers — particularly mid-generation Worcester, Ideal, and Vaillant models — have two or more indicator lights rather than a screen. The fault is identified by the combination of which lights are on, off, or flashing, and at what speed. There is no code number to count — you need to match the combination to a table.
How to read it
Look at all the indicator lights on your boiler at the same time. Note the state of each one: fully on, fully off, flashing slowly (roughly once per second), or flashing fast (four or five times per second).
Some boilers label the lights (e.g. "Central heating demand", "Hot water demand", "Lockout reset"). Others use coloured lights (blue, green, red). Note both the colour and the state.
Look up the exact combination in the fault code table on your model's page. Each combination maps to a specific fault.
Common indicator light brands
Worcester Bosch (24/28CDi II, 25/28Si, Greenstar 24i Junior, 25Si), Ideal (older Mexico/Icos), Vaillant (older Turbomax/EcoMax), Glow-worm, Vokera
Already pressed reset?
Pressing reset clears the displayed code and tells the boiler to attempt a restart. If the boiler fires up successfully, the code is gone until the fault recurs. If it locks out again, the code will reappear.
Boiler locked out again
The same fault has recurred and the code will be showing again. Note it down now before resetting a second time.
Boiler is running normally
The fault may be intermittent. Keep an eye on it — if it returns, note the code immediately. Do not reset repeatedly without addressing the underlying cause.
Check for a fault history menu
Some modern boilers store recent fault codes in a diagnostics menu. Worcester Bosch and Vaillant ecoTEC models often have this — press and hold the mode or service button for a few seconds, or consult your boiler manual for the diagnostics menu shortcut.
When to call a Gas Safe engineer straight away
- › You can smell gas at any point
- › The boiler makes a loud bang, hissing, or banging noise
- › There is visible water leaking from the boiler
- › The fault code reappears immediately after every reset
- › You are unsure what the code means or how serious it is
Found your code?
Search your boiler brand above for a full explanation.