Adding complexity: 1978 Toyota Cressida switch used futuristic fiber-optic system for indicator light

1978 Toyota Cressida Overdrive Switch bulb assembly, installed

How do you ensure that a switch knob’s indicator lamp keeps functioning for, oh, 40 years?

I’m building a car-parts-based boombox shaped like a robot from the Golden Age video game, “Berzerk,” and the project was lacking the all-important master power switch. I wanted a pull-out switch from no later than about 1980, preferably with built-in indicator lamp.

1978 Toyota Cressida in junkyard

I visited the San Francisco Bay Area last week, and I spotted an extremely rare 1978 Toyota Cressida in a self-service wrecking yard there. The car was too picked-over to be worthy of inclusion in the Junkyard Treasures series, but it did have one switch left on the dash: this seriously cool-looking transmission overdrive switch. This was exactly the kind of thing I needed for my boombox project, so I bought it.

1978 Toyota Cressida overdrive control switch

The switch assembly seemed a bit odd, stretching nearly five inches and featuring a mysterious spring-loaded device on one end. The metal components were very substantial, the switch body had a thick molded-plastic moisture shield covering the guts, and entire thing seemed made to last far beyond the lifespan of even a Toyota luxury sedan. When I got it home and bench-tested the switch function, the contacts were a bit iffy so I removed the moisture shield, dismantled the mechanism, and cleaned the internal contacts.

1978 Toyota Cressida overdrive switch light bulb assembly

Once I dismantled the puzzling device on the end of the switch’s sliding shaft, it all became clear. The shaft is hollow, with a light bulb at one end and the switch knob at the other, and a fiber-optic rod is used to direct the light to a hole in the knob. The BA7S light bulb was burned out, of course, so I had to order a replacement.

Fiber-optic rod in 1978 Toyota Cressida overdrive switch

There were other car companies using illuminated pull-out-knob switches during the 1960s and 1970sā€” for example, BMW and Volvoā€” but their designs involved fiddly little light bulbs inside the knob, complete with fritz-prone sliding connectors and the certainty that the illumination mechanism would fail within a decade or two. To Eiji Toyoda, this must have been unacceptable (never mind the fact that an indicator lamp separate from the overdrive switch would have worked just fine), and so this much more robust design was used in the Cressida.

1986 Toyota Camry overdrive switch

Eventually, Toyota’s engineers decided that the automatic shifter handle was a better place for the overdrive switch, and that’s where it lived starting in the middle 1980s. The indicator ended up on the instrument cluster, which is admittedly the more logical location but lacks the futuristic appeal of the earlier fiber-optic indicator switch.

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