Intermittent Spark? Your HT Ignition Lead Is Probably the Problem

What is an HT ignition lead?

HT stands for high tension — high voltage. It is the wire that carries the spark pulse from the piezo igniter to the electrode at the burner.

It looks like an ordinary wire and it is not. It carries tens of thousands of volts in a very short burst, which is why it has thick insulation and why that insulation is the thing that fails.

Why is an intermittent spark almost always the lead?

Because a lead can fail partially in a way that other parts don't.

An igniter either clicks or it doesn't. A ceramic is either cracked or it isn't. But a lead sitting in a hot, greasy, vibrating cabinet degrades gradually:

• Insulation hardens and cracks with heat, so the pulse starts leaking to earth along the way — sometimes, not always, depending on how hot and humid it is.
• Connectors work loose with vibration and thermal cycling. A half-seated bullet makes contact when cold and loses it when everything expands.
• The lead rubs against a metal edge and wears a track through the insulation.

That is the recipe for a spark that works first thing in the morning and fails at 7pm on a Saturday.

How do I test an HT lead?

With the gas isolated and the appliance cold:

1. Look along its whole length. Cracks, hardening, melted patches, rub-throughs against metal edges. Any of these means replace it.
2. Check both ends are fully seated. Push each connector firmly home. A surprising number of "faults" are a bullet sitting half in.
3. Watch it spark in the dark. If you can see arcing anywhere along the lead's length, or where it touches the chassis, the insulation has gone.
4. Check the routing. The lead must not run tight against hot metal or sharp edges.

Leads are the cheapest part in the ignition chain. If a lead looks marginal, replace it rather than chase the fault twice.

Which lead do I need?

Match the terminals at each end and the length. The ends are frequently different from each other, which is why people order the wrong one.

If you are not certain what you have, buy the universal 1000mm kit at £9.99. It ships with 2.4mm and 4mm female bullets plus adapters, so it covers the great majority of commercial gas ignition setups, and you can cut it to length.

Browse HT ignition leads

How do I fit one?

1. Isolate the gas, let it cool.
2. Photograph the routing of the old lead before you remove it. Routing matters — see below.
3. Pull the old lead off at both ends.
4. Fit the new one and push both connectors fully home until they seat.
5. Route it away from hot surfaces and sharp edges. A lead pressed against a hot casting will fail again in months.
6. Leave a little slack — a lead pulled taut will work its connectors loose.
7. Restore gas and test the spark before closing up.

UK commercial catering gas work must be carried out by a Gas Safe registered engineer qualified for commercial catering.

Frequently asked questions

Can I use ordinary wire instead?

No. Standard wire is not insulated for the voltages involved. It will arc through to earth almost immediately, and it is a fire and shock risk. Use a proper HT lead — they cost £5.99.

Can I shorten a lead that is too long?

A universal kit is designed for it. Don't leave a long lead coiled up against hot metal — either route it properly or fit the right length.

My spark works when cold and fails when the appliance is hot. Why?

That is the signature of a degraded lead or a loose connector. Heat expands the metal and hardens the insulation, so a marginal connection or a cracked sheath fails exactly when the kitchen is busiest. Replace the lead.

I replaced the igniter and the electrode and it still won't spark reliably.

Then it is the lead — it is the only part of the chain left. It is also the cheapest, which is why it is worth doing first, not last.

How fast can I get one?

UK stock from £5.99. Order before 10am for next-day delivery, free over £25. Call 073 8051 5838.

Fix the whole ignition chain at once

Igniter, lead and electrode together come to under £35 and take one visit rather than three. If your ignition is playing up and the appliance is old, replace the set.

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