Boiler Is Not Firing Up or Firing Up Randomly

Diagnose & Fix Intermittent Boiler Issues Quickly and Safely

If your boiler isn’t firing up at all—or only does so randomly—you’re likely dealing with a frustrating and potentially serious heating issue. Whether it’s leaving your home cold or giving you inconsistent hot water, this problem should never be ignored.

At A&C Heating and Plumbing Ltd., we’ve seen it all. Below is your practical guide to understanding what might be wrong and how to fix it—or when to call a professional Gas Safe engineer.

❌ Common Symptoms:

• Boiler makes clicking noises but doesn’t ignite

• Boiler starts, then shuts off suddenly

• Heating works sporadically

• Hot water works inconsistently

• Display shows fault codes (e.g. F28, F29, L2)

🔎 Top Reasons Why Your Boiler Is Not Firing Up (or Randomly Firing)

1. 🔁 Ignition Failure

Ignition issues are a common cause for boilers not firing up. If the boiler tries to ignite but fails, it may lock out.

Possible causes:

• Faulty ignition electrode

• Weak spark

• Low gas pressure

• Flue blockages

🛠️ Solution: A Gas Safe engineer can test the spark electrode and ignition sequence.

2. 💧 Low Boiler Pressure

If your boiler pressure is below 1.0 bar, the system may not ignite.

🧰 Fix:

• Check the pressure gauge

• Re-pressurize using the filling loop

• Aim for 1.2–1.5 bar

📉 Still not firing? Check for leaks or call us to investigate.

3. 🚿 Faulty Diverter Valve (Combi Boilers)

If your hot water works but heating doesn’t (or vice versa), your diverter valve may be stuck or faulty.

🔧 Only a professional can clean or replace this part.

4. 🌡️ Thermostat or Timer Faults

Your boiler won’t fire up if it doesn’t receive the correct signal from the thermostat or heating programmer.

🔌 Check:

• Room thermostat is above ambient temperature

• Timer is correctly set

• Batteries (if wireless) are fresh

• Smart thermostats are connected to Wi-Fi

5. ❄️ Frozen Condensate Pipe (Common in Winter)

Condensate pipes can freeze in cold weather, causing the boiler to shut down.

💡 Tip: Pour warm water (not boiling) over the pipe or use a heat pack to thaw it.

6. ⚠️ Faulty PCB (Printed Circuit Board)

If your boiler fires up randomly or keeps turning off, it could be a malfunctioning control board.

👨‍🔧 This is a complex and expensive repair—best handled by a certified heating engineer.

📟 What Boiler Fault Codes Mean

Some common fault codes for firing issues:

🧠 Use these codes to help diagnose—but never attempt a gas repair unless qualified.

🧰 We Repair All Major Boiler Brands:

• ✅ Ideal

• ✅ Vaillant

• ✅ Worcester Bosch

• ✅ Baxi

• ✅ Glow-worm

• ✅ Ariston

• ✅ Ferroli

📍 Areas We Cover:

We offer fast callouts across North and West London, including:

🔹 North London:

Barnet, Finchley, Kentish Town, Camden, Edgware, Haringey, Enfield

🔹 West London:

Ealing, Hounslow, Chiswick, Brentford, Acton, Wandsworth

🛠️ Why Choose A&C Heating and Plumbing Ltd.?

• ✔️ Fast diagnostics and repairs

• ✔️ Fully Gas Safe Registered

• ✔️ Ideal and Vaillant specialists

• ✔️ Emergency callouts available

• ✔️ Transparent pricing & trusted local service

📞 Need Help? Book a Heating Engineer Today

Stop putting up with unreliable heating. Let our expert team get your boiler firing up properly—and safely.

📲 Call Us Now: 0779 559 5757
🚨 24/7 Emergency Boiler Repairs Across London