It was a hot summer day and the humidity was high in the shop when I starting working on one of my regular customer’s new found gems. It was a late 50’s Chrysler, a big old boat of a thing with lots of bells and whistles under the hood and dash. Nothing was added, everything was original and in fairly good shape. You could tell this car has never been left outside for any length of time. The paint finish showed no signs of aging or fading. The interior was very clean, and without a single defect. Even the carpet and headliner had that new “old” look to it.
He wanted me to go thru the electrical components on the car and see if I could get it all in working order. It had it all, radio, electric seats, power windows, power antenna, and just about anything else they could think of putting on a car in those days. I would try each window switch and each knob on the dash to make sure everything worked correctly. The turn signal indicators blinked on the tips of the fenders as well as in the dash. The heater blower motor hummed as if it was brand new. All the speeds worked on the wipers and even the reverse lights worked. It was truly a time piece of early Americana ingenuity.
The only thing I found “not” working was this contraption under the hood. It was about the size of a shoe box. I took the cover off of it to see what all the wires were leading to. Inside the box were several early glass vacuum tubes and a dusty old circuit board with a few resistors and what appeared to be a voltage controller of some sort. Luckily, the new owner had the factory manuals with the car. Even the manual was well taken care of. Not a single torn edge or creased page. I carefully went thru the old manual so as to not do any damage to this priceless book. In the back section were all of the wiring diagrams right down to the size of the resistors on the circuits. (Let’s see the manufacturer put that info out these days…)
I studied the diagram carefully and found out what this thing was. It’s an early automatic dimming headlight system. Way cool, wow, I’ve never seen one of these. But I could tell by just reading the prints how this thing worked. I went straight to solving the problem. Luckily (I think) I’m old enough to have had some training in the old TV tube era. Those classes sure were coming in handy now. It really didn’t turn out to be all that bad. The photocell in the front grill was disconnected, and the shoe box of tubes was in need of cleaning and attaching all the connectors back onto the board.
I reached in and turned on the “auto” system… the tubes started to glow… wow… this is exciting! (Can ya imagine… a grown man getting a thrill out of watching old TV tubes warm up… I really need to get out in the real world a little more often…). There was a hum and a crackle of the tube grids… I could hear the unmistakable sound of the tubes coming up to temperature. The humming subsided a bit, and leveled off to a light electrical buzz of an old TV set. By now I was expecting to see the headlights come on by themselves. Nothing, nada, zip… crud… it’s still not working. I went back to the old manual and followed the diagram some more.
At the very bottom edge of the page it showed a single lead going to the floor dimmer switch. Ok, I guess I’ll look there. By now its mid afternoon, and the humidity level in the shop is at its highest. I’m all hot, sweaty, and probably a little dehydrated. I stretched across that huge metal threshold and pulled the carpet back. Lying right there next to the dimmer switch connection was that single wire. I plugged it in… waited a second… nothing… so I reached over and pushed the dimmer switch with my hand. JumPin’ Gee’ ZaPPin’ ZING! WTF was that! I was jiggling around as if I was holding onto the electric fence at my Granddad’s farm. Now I know exactly how bacon feels when ya throw it into that hot skillet. I’m glad nobody saw me, because I probably looked like a fish flopping out of water the way I was wriggling around. HOLY Shhhhht! That smarts! ! !
After the ringing in my ears and the tunnel vision vanished, and everything returned back to normal I gave up on the wiring diagram and instead read how the system worked in the front section of the book. It turns out that driver’s “soled” shoe acts as the final ground to activate the system. It used a high amperage circuit to make the connection between driver and the automatic control unit out under the hood. To activate it you merely rested your foot on top of the dimmer for a moment. I guess if you were barefoot… you’d be in for quite a shock. It’s probably why the whole thing was disconnected in the first place. But, I’ll have to say… it does work, the headlights will dim and come on by themselves.
Just don’t lay on a metal threshold on a hot humid day… all hot and sweaty, then grab hold of the dimmer switch with your sweaty palm… cause it won’t be lights on… it’ll be LIGHTS OUT!