LUCAS, The prince of darkness....

Some words about Lucas electrics or at least the original electrical system of a Lotus Seven S2…

Axiom 1: Lucas electrical systems abide by Murphy's law.
Axiom 2: The Lucas electrical system is totally predictable from the stand point that one can be absolutely sure that the system WILL fail at the worst time.
Axiom 3: If Lucas made guns, wars would not start either.
Axiom 4: Why do the English drink warm beer? Lucas made the refrigerators, too.
Axiom 5: The Lucas motto: "Get home before dark."

With these 5 thoughts in mind you can imagine the messy nest of tangled wires that I inherited. There were splices, joints, color changes, dead end wires, all oil soaked or burnt. It didn't take me long to realize that this mess was not going back into the car.
Then there's the fuse box that holds two 35 amp slow blow fuses. Anyway, back to the story, it was clear that the previous owners had tried to keep things going by splicing and adding wires. I had a choice, try to restore the original system or re-design the whole thing.
One thing for sure, if I restored the system to original I would retain all the original problems! I decide to re-design the whole thing! I sketched out a circuit diagram and refined it about 5 or 6 times until I had a system that I believed would be reliable.
The new system has 5 fuses all about 10-15 amps each. The system breaks down the wiring harness into modules, 4 in total. This provided a neat engine bay and kept most of the wiring away from the heat and oil of the engine.

All wires were upgraded to today's standards:
1.0mm² for basic lighting, tail, brake, side, etc.
2.0mm² for headlights and ignition
4.0mm² for starter solenoid and alternator.
16 mm² for battery and starter connections.

I designed the system so that very rarely would any fuse have more than one operating system. For example, the fuse which carried the radiator fan also protects the wipers - logical? The radiator fan is used on hot days and when it rains it's cool.


Major colour groups are as follows:

Black Reference Earth (ground) connections
Brown Hot all the time, unfused Main battery feed, Alternator circuits
Purple Hot all the time, fused Horn, Electric fan
White Hot with ignition on, unfused Ignition coil, Fuel pump
Green Hot with ignition on, fused Indicators, Stop light, wipers

Secondary Circuits:
Green Red Indicator switch to left-hand flasher lamps
Green White Indicator switch to right-hand flasher lamps
Green Purple Stop switch to stop lamps
Blue Red Switch to Low beam head lamp
Blue White Switch to High beam head lamp
Red Red Light switch to side lights and no. plate light
Red Green Light switch to Head light swítch

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