27. April 2026

Your Boiler Is Lying to You (And Why Most Engineers Believe It)

You reset your boiler. It fires up. Heat returns. You breathe out. Three hours later – red light. Cold radiators. Dead.

You call an engineer. He arrives. The boiler works perfectly while he watches. He shrugs. "Could be anything. Call me if it happens again."

It happens again. At 11pm. On a Sunday. In December. This is not bad luck. This is your boiler lying. And most engineers believe the lie.

Why Intermittent Faults Are a Nightmare

A boiler that works sometimes is harder to fix than a boiler that is completely dead. Why? Because the fault hides.

A failing sensor might work perfectly when the boiler is warm – then fail when it cools down
A cracked PCB might work for hours – then lose communication with the fan
A gas valve might stick – but only once every 50 cycles

Most engineers arrive, see the boiler working, run a quick safety check, and leave. They didn't fail you. The boiler lied. And they didn't know how to catch it.

What Forensic Diagnosis Looks Like

I don't guess. I don't "try a part and see." I use forensic diagnosis.

Multimeter tests on every component – proving what works and what doesn't
Flue gas analysis – reading the boiler's "breath" to detect hidden issues
System-wide inspection – because sometimes the pipes, pump, or gas supply are lying too

I worked in commercial heating before London. Massive systems where a single fault could shut down a whole building. You don't guess there. You prove.

I also worked for Vaillant, Worcester Bosch, and Ideal Boilers. Factory training. I know exactly where their boilers hide their secrets.

The £30 Sensor That Saved £3,500

A customer in East London called me. Three engineers had told her she needed a new boiler. Quotes between £3,000 and £4,500.

I spent two hours. I found a failing thermistor – a £30 sensor that was telling the boiler the wrong temperature. The boiler wasn't dead. It was just confused.

I replaced the sensor. The boiler has worked perfectly for two years. She saved over £3,000. That is the power of forensic diagnosis.

Signs Your Boiler Is Lying to You

Here are the most common lies boilers tell – and what they really mean:

Locks out only in cold weather → Condensate pipe frozen or blocked
Works after reset, then fails hours later → Failing PCB or sensor
Works fine for days, then fails overnight → Gas pressure fluctuation
Noise when heating starts, then goes quiet → Sludge in system or failing pump

These are not mysteries. They are clues. You just need an engineer who knows how to read them.

What to Do Before You Replace Your Boiler

If an engineer tells you that you need a new boiler, ask these three questions:

"What specific component has failed?" – Not "it's old" or "it's inefficient". A specific part.
"Can you show me the test result?" – A voltage reading, a resistance value, or a gas pressure number.
"Can I get a second opinion?" – Any honest engineer will say yes.

I offer a Second Opinion Service for exactly this reason. I will come to your home, run my own forensic diagnosis, and tell you the truth.

Sometimes you really do need a new boiler. I will tell you that honestly. But often? It is a £30 sensor, a £150 pump, or a blocked pipe.

London – I Come to You

I am based in SE27. I serve all London homes within 10 miles. Same-day visits for emergencies. Evening appointments available. No call centres – you speak directly to me.

Call KRS Integrated Services now: 020 3355 4802

Email: info@krsintegratedservices.co.uk

Gas Safe Registered: 978631

Serving London within 10 miles of SE27