Lucas – Prince of Darkness, or just a bad rap?

Lucas harness smoke

Lucas - Prince of Darkness, or just a bad rap?

Like most British based cars, Cobra’s used Lucas electrical components. We’ve all heard the jokes about Lucas Electric

      • Prince of Darkness
      • Lucas 3 position switch: Dim, Flicker and Off
      • Corporate motto: Get home before dark

But maybe ole’ Joseph Lucas got a bum wrap and it is being perpetuated by inferior knock-off products for the restoration market.

The basic design of the Lucas components is generally good, although it may not be to the current aero-space standard. The switch contact may be designed to handle 5 amps but maybe not to the cycling standard that some present day switches are so it wears out sooner.  Europeans don’t use their vehicles as much as the Americans. His designs were for that market, not the current US market.

Couple with that, the automotive ‘hot rod’ market tendency of bigger is better. The car has that 5 amp Lucas switch. Then the owner adds a 20 amp fan in the circuit and the switch fails (because it was overloaded by four times). Is that failure due to Lucas or to the modifier? Add in the propensity of cheaper import products, cutting corners to have the ‘cheapest price’. So the 5 amp switch is modified to reduce costs and now only handles 2 amps. Again, is that a Lucas issue or the knock-off manufacturers fault?

Period Correct, LLC  supplies Lucas branded products rather than less expensive clones. Yes, there are cheaper electrical products out there. We choose not to participate in the ‘how low can you go’ pricing game. Quality and originality is more important. 

There is also a responsibility on the builder/modifier to use the product in an properly designed circuit. It is important the component not be overloaded, both in maintained contact or switching. The component you are controlling may only use 5 amps but what is the in-rush current when the item is switched on? Probably more like 10-20 amps. So how long do you expect a 5 amp switch to hold up. It will arc as the higher amperage flows across the contacts until such time as the contacts weld themselves shut. We recommend doing complete research and proper circuit design to allow for this. 

If you are controlling an item of 7amp load, how much safety factor should be used in the circuit design. Engineers study this for years and determine complex formulas, others say 2-3 times the load – it becomes an art and a science. Using a liberal design factor of 2 times, the switch controlling your 7amp item would be rated at 15amps. 


But no one makes a 15amp Lucas switch – control the circuit with a relay where you can get the contact rating needed and then control the relay with the Lucas 5amp switch. Hide the relay from sight, use the period correct Lucas switch on the dash and both components will function and perform like you want. Cheat the process, try to use the 5amp switch with the 15amp fan and you will eventually pay the price – the only unknown is how long it may last. Might be the first try, might be the 28th time, the time you’re miles away from your shop and now facing a towing bill go get home.

Bottom line: Lucas makes some very good products. Be sure they’re Lucas and the design is proper. Pay attention to product specifications and circuit amperage loads.

Want to look like the 'real' thing?

We carry a full line of Lucas switches and relays, as used on the original Shelby cobra builds. Click to view the catalog.

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