HT Leads Replacement

Mobile HT lead replacement at your home or office, to cure misfires, rough running and a damp weather starting problem.

Book Your
Car Service

icon-whatsapp

Pricing

Pricing varies based on your vehicle

Get a Quote

Service Info

Typical Duration 1 hour

We test the existing leads for resistance and breakdown, replace them as a matched set with the correct lengths in the correct firing order, inspect the plugs, distributor cap and rotor arm where fitted, and restore the original routing and clipping.

Skip the garage, our master mechanics come to you

At your home or office
Fair & transparent pricing
6-month, 6000km warranty

The Most Trusted Mobile HT Leads Replacement

High tension leads carry the ignition voltage from the coil or distributor to each spark plug, and they have to contain tens of thousands of volts along their whole length. As the insulation ages it hardens and cracks, and the voltage begins escaping to the nearest earth instead of reaching the plug. That produces misfires that are often worse in damp weather, which is the classic signature of a failing lead. Michanic replaces HT leads at your home or office.

Why Choose Our Mobile HT Leads Replacement Services?

  1. The Damp Weather Clue:
    A misfire that is worse on a wet morning and clears as the engine warms is characteristic of leads breaking down, and it is easy to misdiagnose as a coil or sensor.
  2. Replaced as a Set:
    Leads age together. Replacing one and leaving three original leads on an old engine simply moves the fault along.
  3. Routing Restored:
    Leads must be kept apart and clipped in their original positions. Bundled or crossed leads induce voltage into each other and cause misfires.
  4. At Your Home or Office:
    A short job done where the car is parked, without a workshop trip.

Why We are the Best Choice for Mobile HT Leads Replacement

  • Correct Lengths and Order:
    Leads are supplied as a matched set with specific lengths. Fitting them in the wrong order produces a badly running engine straight away.
  • Plugs and Cap Checked:
    Distributor caps and rotor arms track and corrode, and worn plugs load the leads. Both are inspected as part of the job.
  • Resistance Measured:
    Leads are checked rather than judged by appearance, since a lead that looks fine can be open circuit internally.
  • Boots Seated Properly:
    Each boot is confirmed clicked onto the plug, because a lead that looks connected but is not seated causes an intermittent misfire.

When an HT lead breaks down, the voltage does not simply disappear. It arcs to the nearest earthed metal, which means that cylinder does not fire and its fuel charge passes into the exhaust unburnt. That is the same damage path as any other misfire, ending at an overheated catalytic converter. Leads that arc also stress the coil, which now sees an open circuit rather than a proper load, and coils fail from that. Damp weather makes it dramatically worse because moisture provides the path the voltage was looking for.

Frequently Asked Questions

  • What are the symptoms of faulty HT leads?
    Misfiring, rough idling, hesitation, hard starting and poor economy, characteristically worse in damp weather. Visible arcing can often be seen at night with the bonnet open and the engine running.
  • Why is my misfire worse when it rains?
    Moisture provides an easy path to earth for voltage escaping through cracked insulation. On a dry day the lead may just hold, and on a damp morning it does not, which is why the fault appears and disappears with the weather.
  • Should HT leads be replaced as a set?
    Yes. They have aged under the same heat and voltage, so replacing one lead on an older engine usually means another fails shortly after. Sets are also matched for length, which keeps the routing correct.
  • Do modern cars have HT leads?
    Many do not. Engines with coil on plug ignition have a coil sitting directly on each spark plug and no leads at all. Leads are found on older engines and on some designs using a coil pack with separate leads.
  • Can bad HT leads damage the ignition coil?
    Yes. A lead that has gone open circuit or is arcing to earth leaves the coil without a proper load, and the resulting voltage stress breaks down the coil insulation over time.