car_battery

The Dark Side of Positive Earth

British sports cars were wired really, really weirdly (Say that 5 times.) The earth was negative on every American car I had ever forced an 8-track tape player into, and I was sure that my skills could be applied with no less success on the Austin America I had just acquired. After all, it said “America” right on the fender badge! But I had a problem…this car was wired positive earth.

These were the days of no Internet Googling and no good sense on my part. That did not deter me. I decided to fool mother earth into thinking that my 8-track tape player was correctly wired in the incorrectly wired Austin.

The 1965 Austin America was not your typical college transport in 1977. Just twelve years old, it had already proven itself to be the “clown car” on campus and the butt of many jokes… all of which I endured patiently with the satisfied smugness of knowing that my car was British and required a “stiff upper lip” from its owner.

I tackled the 8-track task with initiative and creativity. First came the box—a thin shell of wood and wood by-products that precisely fit the size and shape of my “Kraco” deluxe with fade control and three-speaker capability. This box would isolate the entire head unit from the dread positive earth Austin America… much like carrying nitro-glycerin in a Styrofoam ice chest strapped to the handle bars of a Norton Commando.

Carefully, with the skill of 007 placing a detonator into a suitcase bomb, I inserted the entire wood-wrapped head unit into the package shelf, just below the Austin’s dash. So far, so good! I ran two wires directly to the battery and squeezed the stripped ends against the lead posts. For good measure, I wrapped everything in yards of black electrical tape.

Now came the first test. I closed my eyes and twisted the volume knob until I heard it “click”. Nothing happened. This was good. I had yet to put an 8-track tape into the head and there were no speakers connected to the unit.

Somewhere in the back of my mind I remembered the advice of my father: “Be sure to disconnect the battery when making electrical connections on your car.” I heard this as a distant eerie voice… part Darth Vader, part Yoda. (I had just seen Star Wars the week before.) I obeyed the voice and disconnected the battery. The Force was with me on this job!

The installation of the speakers was quick and carefree. The front speakers went under the bucket seats, the wires running alongside the seat adjustment tracks and the single rear speaker fit nicely on the package shelf in back. Rather than run ground wires from the head unit, I chose the much simpler method of grounding each speaker to the body.

I was ready for the “krackin Kraco” to krank out some serious tunes! After reconnecting the battery I looked though my 8-track collection and selected an appropriate artist… Grand Funk Railroad! I shoved the tape into the head unit, twisted the volume knob to “on” and waited for the percussion of bass and treble.

“BOWZZZfzzzzzzchTTTzzzzztffffazzzzZCHtehzzzzzZZZzz!!!!!!!”

 

And so, I learned an important lesson: “You can’t fool mother earth.” My speakers were grounded to the positive earth of the Austin’s body while the head unit was grounded to the negative earth of the battery. The result was an explosion of “Earth, Wind, and Fire” (to name another 70’s rock band). Like a whirling dervish I clawed at the wiring, casting each smoking speaker from the car and extracting the head unit with one violent jerk.

The Austin and I soldiered on for the remainder of the year, but a foreboding silence was between us. I finally sold her away… and with her went the innocent lesson of the “negative side of positive earth.”

By Ric Glomstad

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'The Dark Side of Positive Earth' have 14 comments

  1. July 17, 2012 @ 9:10 pm j c glomstad

    Son: one valuable lesson you did not learn, You have to isolate all the units. It can be done. Better luck next time. Dad

    Reply

  2. July 20, 2012 @ 10:22 am Michael Carnell

    My 66 Vanden Plas Princess, a sister model of that Austin America, has positive earth and I plan to keep her that way. But you have to beware!!

    Reply

  3. July 27, 2012 @ 2:24 am George King

    I’ve got a 1968 Wolseley Hornet Mk 3 (ask yer mum ), he’s now negative earth so I could fit LED’s in his brake / tail lights. 1/3 the current, 300 times the light up speed. I can also fit an electronic ignition later as well. I want to keep the little fella original but he’s got drum brakes in a disc brake world so following cars need notice of the stopping power of the lockheed twin leading shoe drum.

    Reply

  4. July 27, 2012 @ 3:27 am Jose

    it is easy to convert to Neg. Ground. I did it to my ’65 Jaguar with no problems.

    see how it is done from a pro: http://www.starautoelectric.com/page25.php

    Reply

  5. July 27, 2012 @ 4:20 am Terry Blubaugh

    Good article Ric, and well written. Most British car enthusiasts have struggled with the concept of positive ground for decades. On a lighter note, your reference to Grand Funk Railroad made me laugh. Back in the 50’s, my wife was the babysitter and neighbor to Max Carl (Gronenthal then). Max, of course, is the current lead singer for GFR, The American Band. We stay in touch with Max, and often see him perform. I shall send him a copy of your article. Perhaps he’ll mention a Healey in his next re-write of his theme song for “Pinks”. Best Regards.

    Reply

  6. July 27, 2012 @ 9:33 am Jeff Cardinal

    I installed an FM stereo in my ’61 sprite similarly, (except I didn’t use the chassis for a conductor). I also had to isolate the ground of the antenna. It worked well, except at louder volumes the radio would start rhythmically start cutting in and out with a bloop-bloop sound. I think it probably had something to do with the ground plane being reversed polarity or something. Shortly after, I discovered that all you have to do to change the polarity of the whole car is to switch the battery terminals and re-polarize the generator. Really! So I did that and the whole problem went away.

    Reply

  7. July 27, 2012 @ 10:38 am Francis

    Just remember one thing my British Motor friends: Lucas, The mother of darkness!!!!!!!!!!!!!!!!!!!!!!!!

    Reply

  8. July 27, 2012 @ 2:03 pm Bo

    I had a ’64 TR4 positive earth. Of course I did the same as you with the wooden box, but I remembered to run both speakers wires to the deck. In goes “Dark Side of the Moon.” It worked!!!
    I wish I still had that car.

    Reply

  9. July 29, 2012 @ 9:57 am Gerald Foster

    You will notice that many MGB models have a sticker that says “IMPRORTANT, This Vehicle is wired NEGATIVE EARTH” They finally figured it out.
    In the 60’s I put a stero in my MGA buy purchasing a box from Radio Shack specifically designed to allow negative earth devices to be wired to positive earth cars. Still have it, but all MG’s I have are converted to negative ground.
    Cheers,

    Reply

  10. July 30, 2012 @ 12:04 pm Charly

    I have over a dozen British cars and 1 British bike and all except the bike have been converted to neg. ground. Just to let you know, I’ve had the same issue with American cars of the same era. The one I recall was 54 Ford F-100 pick-up, with a slide out mount, which made it all easier.
    The question I have is why were they postive ground in the first place and why did it get changed to negative ground? This doesn’t apply to just LBC, but mosy early autos.
    I was tols once that the positive ground cars didn’t get as dusty as easily and they also resisted rust, I just accepted this as myth. Any thoughts?

    Reply

  11. August 2, 2012 @ 7:08 am Tony

    There’s nothing wrong with positive ground (positive earth). That system was used by Ford, Chrysler, many tractor manufacturers like John Deere and New Holland, and many large truck manufacturers like White, Peterbilt, Mack and Kenworth. It helped increase the life of points and the gap of spark plugs remained uniform. The solution to putting modern sound systems and accessories in our British cars is to get a ground inverter, found many times at truck stops and can be gotten thru some electronics stores. Otherwise, you might be best to convert to an alternator and change the ground/earth to negative. There is a good reason for that change: many newer car sound systems require more power and an alternator will solve it. Most alternators work on negative ground/earth with few exceptions.

    With regard to Lucas….it’s probably the best system ever designed….the color codes are uniform regardless of age and was used throughout the entire British car manufacture from the 20’s to the mid 80’s….if you know your Lucas color codes, you can work on it without a wire schematic. With other wire manufacturers like Bosch and others failed in many ways to create any uniform color code that remained constant for more than 5 years….and you could never be sure what color was ground/earth…including US car companies!

    Reply

  12. April 20, 2018 @ 11:13 am Graham

    I have a 1972 mgbgt. Is this positive or negative earth. I’ve replaced the batteries and can’t remember.

    Reply

  13. February 13, 2019 @ 9:28 am Tom Keenan

    I happened onto this discussion while I was googling positive earth to show a younger tech the glory of the positive earth system. While I don’t have British cars I do have a 1972 Triumph Daytona and a 1976 Triumph 750 Tiger, both of which are positive earth. I found an led tail light for the 72 in England. As an aside I take exception to Lucas being the Prince of Darkness. My wife rides a 1979 Moto Guzzi SP 1000 , which. which being from the continent has all Bosch electrics. My Triumph has had 1 electrical failure in over 35,000 miles in the time I have owned it. The turn signal switch failed. My wife’s Guzzi has had multiple charging system failures in the same time. This has totally changed my opinion of Lucas. LOL I know that the Lucas position is Gentlemen don’t motor about after dark, but my experience over the last 10 years or so has been good. Hope I didn’t jinx myself

    Reply

  14. November 17, 2019 @ 6:58 pm Conrad

    Gentleman’s, it is November 17 – 2019 as I just happened to stumble my self into this page.
    And opted to share with you’ll my 17 year long journey into the Dark Side of Positive Earth Lucas technology.
    After a year long restoration of a 1955 jaguar quite a few years back, and an ongoing Triumph Spitfire project, I fell head over heels for a 1964 Sunbeam Alpine IV.
    The young fallow who sold it to me was never able to get pass the engine cranking experience, so after three years of playing with it he opted to leave it behind as payment of some rental arrears.
    Needless to say.
    My beloved 64 Alpine IV is still kicking dust, and yes, it is running the original 12 volt LUCAS positive earth electrical system, Dynamo and control box.
    Yes, it does still have the generous Two 20 amp glass fuses to protect the electrical system and a 100% functional hand powered crank start option.(Quite a work out)
    And, it also has been retrofitted with a 12 volt Negative earth digital display, remote control, 4 speakers stereo system. (Purchased at Sam Walton’s place)
    An online purchased 12 volt amplified hidden antena. (Yes, no need to drill a hole into the pristine Rootes Body)
    Gosh!!! It hurted me to drill the two doors to retrofit some badly need it side view mirrors (Supplied by Curt at Sunbeam Specialties) Thanks Curt.
    In addition, I’ve also managed to install a Negative earth alarm system under the hood and a wireless remote controlled fuel cut off valve under the car, as an extra security measure. (Conveniently send to my door by the prestigious eBay market place)

    A true pain in the Dark side of yours truly to keep up with the 55 year old secondary throttle SOLEX carburetor, but I love my slug.
    Amazingly it still manages to do zero to sixty in five minutes, yes you read it right, 0-60 in 5 min.
    Well maybe not that bad, since it is still commuting 80 miles daily round trip to and from work, at 80 MPH, along I-40 here in NM.

    It has been a real challenge, often an ugly, nasty, despicable idea of upgrading to Negative Earth Alternator system peeks it’s ugly head into my brain.
    But somehow I’ve triumphantly managed to overcome the suicidal thoughts, and convinced my self to carry on.
    “Yes! sometimes I do speak to my self”….. In search of an expert advice, of course……….. Mind you……

    Gentleman’s! Keep’em on the road…….

    Reply


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