If your Ideal Logic or Ideal Logic+ boiler is failing to ignite, one of the first components a Gas Safe engineer should investigate is the spark generator. Without a strong ignition spark, the boiler cannot light the burner, resulting in repeated ignition attempts and eventually a boiler lockout.

Many engineers remove the ignition electrode unnecessarily, but there is a much quicker way to confirm whether the spark generator is working correctly.

At Certificates4UK Ltd, we regularly diagnose ignition faults on Ideal boilers throughout West Molesey, Esher, Walton-on-Thames, Weybridge, Thames Ditton, Kingston upon Thames, and surrounding Surrey areas. In this guide, we explain how to test the spark generator safely using an AccuSpark tester, helping to speed up diagnosis and reduce unnecessary dismantling.

---

What Does the Spark Generator Do?

The spark generator is responsible for producing the high-voltage electrical spark that ignites the gas-air mixture inside the burner.

Each time your boiler starts, the PCB sends a signal to the spark generator, which creates thousands of volts and delivers them to the ignition electrode.

If the spark generator fails, the boiler cannot ignite, even if every other component is working correctly.

---

Common Symptoms of a Faulty Spark Generator

A failed spark generator may cause:

• Boiler attempting to ignite repeatedly
• Boiler locking out after several ignition attempts
• Clicking noise with no flame
• No visible spark at the ignition electrode
• Ignition fault or flame failure error codes
• Intermittent ignition problems

These symptoms can also be caused by faulty electrodes, gas supply issues, or PCB faults, so testing is essential before replacing parts.

---

Tools Required

To test the spark generator, you’ll need:

• AccuSpark tester
• Digital torch or good lighting
• Basic hand tools
• PPE
• Manufacturer’s service information

An AccuSpark tester is inexpensive and can save significant diagnostic time.

---

How to Test the Spark Generator

Step 1 – Isolate the Boiler

Before removing any covers, isolate the electrical supply and follow all manufacturer safety procedures.

---

Step 2 – Locate the Spark Generator Lead

Identify the ignition lead running between the spark generator and the ignition electrode.

---

Step 3 – Connect the AccuSpark Tester

Connect the tester:

• Clip the tester onto the ignition electrode terminal.
• Attach the spark generator lead to the tester.

No need to remove the ignition electrode from the heat exchanger.

---

Step 4 – Restore Power

Restore electrical power and request ignition.

Observe the AccuSpark tester.

If the spark generator is operating correctly, the tester will flash as the spark is produced.

---

Step 5 – Interpret the Results

Tester flashes

✅ Spark generator operating normally.

Continue diagnosing:

• Ignition electrode
• Gas supply
• Flame sensing
• Burner
• Gas valve

---

No flash

❌ Spark generator likely faulty.

Further testing should be carried out before replacement.

---

Engineer’s Tip

Using an AccuSpark tester allows you to confirm spark output in seconds without removing the ignition electrode.

This reduces unnecessary dismantling and speeds up diagnosis—especially useful when working on Ideal Logic and Logic+ boilers.

---

Other Components That Can Cause Ignition Faults

Not every ignition problem is caused by the spark generator.

Other possible causes include:

• Damaged ignition electrode
• Broken HT lead
• Faulty gas valve
• Low gas pressure
• PCB fault
• Fan failure
• Blocked condensate
• Flame sensing problems

Always follow a systematic diagnostic process rather than replacing components by guesswork.

---

Fault Finding Summary

Symptom	Possible Cause	Recommended Action
No ignition	Spark generator	Test with AccuSpark
Clicking but no flame	Gas valve or gas supply	Check gas pressure
No spark visible	Spark generator or HT lead	Inspect ignition circuit
Boiler locks out	Ignition system fault	Complete full diagnosis
Intermittent ignition	Spark generator or electrode	Test both components

---

Why Accurate Diagnosis Matters

Replacing ignition components without testing can quickly become expensive.

Professional diagnosis helps:

• Reduce unnecessary parts replacement
• Improve first-time fix rates
• Save diagnostic time
• Lower repair costs
• Restore heating more quickly

Testing the spark generator first is often one of the fastest ways to identify the source of an ignition fault.

---

Why Choose Certificates4UK Ltd?

Since 2011, Certificates4UK Ltd has specialised in diagnosing and repairing domestic boilers across Surrey.

Our experienced Gas Safe engineers regularly repair:

• Ideal Logic
• Ideal Logic+
• Ideal Vogue
• Worcester Bosch
• Vaillant
• Baxi
• Alpha
• Viessmann
• Vokera

We provide professional boiler diagnostics, servicing, and repairs throughout West Molesey, Esher, Walton-on-Thames, Hersham, Thames Ditton, Cobham, Weybridge, Kingston upon Thames, and surrounding Surrey areas.

---

Frequently Asked Questions

Can I test the spark generator without removing the electrode?

Yes. An AccuSpark tester allows Gas Safe engineers to check for spark output without removing the ignition electrode, making diagnosis quicker and reducing unnecessary dismantling.

Does no spark always mean the spark generator is faulty?

Not always. A damaged HT lead, faulty PCB, or wiring issue can also prevent spark generation. Further testing should be carried out before replacing components.

Can homeowners carry out this test?

No. Testing ignition components requires access to the boiler’s internal electrical and combustion systems and should only be carried out by a Gas Safe registered engineer.

What happens if the spark generator fails?

Without a working spark generator, the boiler cannot ignite the burner, resulting in repeated ignition attempts followed by a safety lockout.

---