Is this tool actually free?

Yes. No signup, no credit card, no paywall. We ask for your email so we can send the checklist — that is the only exchange.

Which boiler brands are supported?

Every major UK brand — Worcester Bosch, Vaillant, Baxi, Ideal, Viessmann, Glow-worm, Potterton, Ferroli, Ariston, Alpha, Main, Keston, and more. The AI also handles air source heat pumps from Daikin, Mitsubishi, Samsung and LG.

Is the advice Gas Safe compliant?

The checklist never recommends work outside Gas Safe scope. It is structured reference information to speed up your own diagnostic process. Always follow manufacturer documentation and your own competence.

How accurate is the AI?

The AI is trained on manufacturer documentation and common field-engineering knowledge. For fault codes with a single well-documented cause it is very accurate. For vague symptoms with multiple potential causes it will suggest the most likely checks in order — you decide what actually applies.

What data do you store?

Your email, the appliance details you entered, and the generated checklist. If you tick the "publish anonymously" box, we publish the checklist to a public URL with the make, model and symptoms — but never your email or any personal information.

Why do you ask to publish it publicly?

Other engineers searching Google for the same fault benefit from your submission. It is the Stack Overflow model — the community gets stronger with each contribution. You can untick the box if you prefer to keep it private.

Is there a limit on how many I can generate?

To keep the tool free and prevent abuse, we limit submissions to a few per hour per user. If you hit the limit, just wait an hour and try again.

No. We only email the checklist you asked for. If you tick the marketing checkbox we may send the occasional BoilerTag tip or product update — unsubscribe any time.

Free AI tool for engineers

AI Boiler Fault Diagnostic Checklist

Stuck on a fault? Enter the make, model, and fault code — we'll email you a structured checklist you can work through on-site in under 30 seconds.

How it works

1
Enter the boiler details
Make, model, fault code if you have one, and a quick description of the symptoms.
2
Get your checklist
A step-by-step diagnostic list ordered by safety, cost-to-check, and likelihood.
3
Email copy sent
We email you the full checklist so you can refer back to it on-site or in the van.

Tag it once. Get rebooked every year.

Stick a BoilerTag on the boiler. The homeowner scans the QR when the service is due — your name and number are right there. Your first 12 tags are free.

Get 12 free BoilerTags

Frequently asked questions

Recently published diagnostics

Browse all →

Every checklist submitted by an engineer (with consent) becomes a public reference page. Here are the 20 most recent.

Worcester Bosch Greenstar
Frequent pressure drops on a Worcester Bosch Greenstar boiler typically indicate a leak within the sealed system, a faulty pressure relief valve (PRV), or an issue with the expansion vessel. While repressurising the system can offer a temporary fix, persistent drops require a thorough diagnosis by a Gas Safe registered engineer to identify and rectify the underlying cause.
Baxi 800
The Baxi 800 boiler intermittently heating without a fault code can be attributed to several common issues, including low system pressure, circulation problems, or issues with the thermostat or diverter valve. While no specific fault code was provided, common Baxi fault codes related to heating issues include E119 (low pressure) and E125 (circulation fault). It's crucial to address these systematically, prioritising safety and checking the simplest causes first.
Worcester Greenstar Cdi
The Worcester Greenstar CDi is a condensing combination boiler. The symptom of 'won't come up to heat' without a specific fault code can indicate several issues, ranging from basic user settings to component failures. Common causes include low system pressure, issues with the gas supply, condensate blockages, or problems with key components like the fan, ignition electrodes, or PCB. There are no specific service bulletins for a general 'no heat' fault, but manufacturer documentation and reputable trade sources highlight these common failure modes.