Lucas Electrical System Troubleshooting

ARC has a strong background in diagnosing and repairing the notorious Lucas British electrical systems (no offense meant to our friends across the pond!) Have you ever heard a reference to Joseph Lucas, Prince of Darkness? When the lights go out in your British car, you can thank him. All classic British cars use Lucas wiring systems.

The Lucas electrical system is based on isolated grounds rather than chassis grounds calling for two sets of wires for every one used in American cars to do the same thing. Over the years due to the misunderstood nature of Lucas electrical systems, local shade tree mechanics have attempted minor troubleshooting repairs and made quite a mess of the wiring system. A common attempt to fix it is run a new wire and bypass the problem. You can see the outcome in this photo!

Wiring nightmare (after someone tried to fix it).

More wiring mess in the engine compartment.

The grounding system is completely different in British cars than in American cars. Wiring terminals are poorly protected in older systems allowing corrosion to occur in contacts and terminals. England’s damp climate coupled with the exposed terminals, demands regular cleaning and maintenance of contacts and terminals. Something that is not part of “maintenance” in most American cars.

The Jensen is a hybrid using both British and American parts. The engine and drive train is Chrysler, the electrical is the British Lucas system. This vehicle’s wiring was completely restored using the original factory wiring schematics and all contacts and terminals cleaned and dialectric grease applied.

  
Tidy and fully functional engine wiring after restored using factory wiring schematic.

Electrical problems cured.

This specific vehicle is too much fun to drive to be considered for concourse restoration, although it’s rarity makes it tempting. There were only 6300 Jensen Interceptors made and fewer than 3000 reportedly still in existence at last tally. A clean restoration with a few minor improvements and proper maintenance will keep this car on the road for many more years.