Concerning Lucas electrics and Zenor Diodes, there is one thing not mentioned on the web site: ALWAYS make sure the Battery has a GOOD GROUND connection. At both the battery post and the frame connection. No corrosion allowed. (first wash with solvent, then Bicarb of soda), scrape, sand, bolt up and cover with grease (Silicon grease if you have it). There are now available, some neat, Hi-Temp greases associated with auto disk brakes.
The reason this is so important: When there is a bad ground, you have resistance. When you have resistance, to obtain proper amperage (current flow), there is an increase in voltage (pressure). With this excessive increase in voltage ( the zenor opens at 13.5 volts if I recall) the zenor is dumping to ground constantly, creating a lot of heat. This destructive temperature causes that expensive little goodie to fail.
When working for Triumph, in 1970, we held a Dealers Mechanics school in Okl. City. Dennis Manning (BUB Pipes) of Bonneville Streamliner fame, was the instructor. Okl. City was on interstate 40 and was the the main, summer time, conduit from West coast to East coast (or the marijuana filled creek beds of Kansas). All the Hippy Dippies and other pond scum, came rattling down the pike on their jury rigged, death trap, Choppers with their dirty leg gals on the back. Being cool, they were cruising back & forth from coast to coast, getting sunburned, playing "Easy Rider" and avoiding their creditors.
One of my OKC dealers was close to said interstate. They got a lot of chopper trash, traffic with guys wanting to trade "The services of their scaggy passenger, aka. Giving everyone in the service dept a "Hot Water Skull Job", in exchange for a new rear tire or chain. His main mechanic, "Leeroy", was a slightly tattooed, down home, nose picking, crotch scratching, Harley rider with a slight speech and pronunciation defect ... He spoke out, "Why do these here Zen-E-R Die-odes cost so much money ($23 at that time)? The customers think I'm uh try'n to rob'um when I tell 'um they needs uh new Zen-are!" There was a group murmur, validating his query. Dennis went into a technical dissertation, explaining the Zenor was really an electrical valve: manufactured to complete a circuit at a predetermined value of EMF. When the EMF exceeded this predetermined voltage, the molecular construction of it's internal components changed: thereby causing the "valve" to establish continuity to the outer body and/or ground.
Leeroy's (that really was his name) eyes glazed over for a moment. His eyebrows worked up and down a few times, as he mentally tried to digest all these "Physics Class", unfamiliar, technical terms. He closed his slackened jaw, stood up and asked, "Have yew ever tried to Ex-plain, Mo -lek-uh-lar Con-stuck-shun to a 'Hells Angel'? ... Everyone in the room, including Dennis, exploded with laughter. Leeroy stood there, beaming proudly, over having made a "Funny".
Dennis would start to simplify his explanation and then self distruct with laughter. After three of four tries, he wiped his eyes and said, "Tell the dumb son of a bitch, It's a top secret. If you told him, then you would have to kill him!" A still grinning Leeroy, sarcastically said, "Even kidding around, I'll be damned if I'm goin'' to tell a Hells Angel that, I was a-gonna kill 'em. 'Spes-lee with three or four of his buddies standing around."
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Revised: January 05, 2018 .