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> battery connection screw up
dt4
post Jan 14 2020, 02:56 AM
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No radio fitted at present so don't have that to worry about (IMG:style_emoticons/default/idea.gif)
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Superhawk996
post Jan 14 2020, 06:07 AM
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QUOTE(DickSteinkamp @ Jan 13 2020, 11:13 PM) *

Electricity is somewhat of a mystery to me so bear with me.

I don't understand how switching the + and - leads can cause a dead short and burn up wiring. I can understand how polarity sensitive devices (like a diode) might be harmed but why wiring?

Also, there is so very little that gets power with the key in the off position. How would the radio (for example) be damaged?


Most basic answers:

1) Since chassis is assumed to be ground, it can basically source infinete electrons (in theory) and those electrons moving = current. The chassis ground strap between the body and the transmission for example is about 1" wide and is pretty thinck braided wire that can easily handle several hundred amps drawn though it upon cranking and to run the coil and alternator. When the connections are switched (+ for negative) now all the positive wires become ground. Current goes looking for a ground path where ever it can find it - electricity always tries to follow the path of least resistance. If that path happens to be a small gauge + wire that was only sized for 1A but is now trying to support 10A of current draw being drawn through it, poof it melts.

1a) IF, every circuit had an equally sized positive and negative (ground) wires, this situation wouldn't occur. However, that isn't the way cars are wired. Often there is only a positive wire that feeds the circuit and the ground path is provided by "chassis ground". Now you have an asymetric sizing between positive and negative current paths. Positive is limited by wire size. Chassis ground is very large.

2) Electronic componenets like diodes. A diode is only designed to flow current in 1 direction. Diodes have a characteristic called Peak Inverse Voltage (PIV). A diode will resist reverse current flow up to the PIV but beyond that it will "leak". The rate of leakage depends on how much higher the PIV is and whether or not the diode overheats and fails open. As it continues to "leak", allowing current to flow backward, that situation becomes a basis for situation #1. Small gauge + wires can melt since they weren't sized for that current. Really big and well heat sinked diodes (i.e. the alternator) can have some substantial leakage before the overheat and eventually fail open. What circuits flow current in reverse up until the diode opens is up to the electrons trying to find their way home is somewhat of a guess (IMG:style_emoticons/default/sad.gif)

You are correct that if a circuit was completely turned off and has no circuit path, it would be unafffected, unless there are diodes in that circuit that fails, and, creates a path where otherwise it would not have existed when connected properly.
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Superhawk996
post Jan 14 2020, 06:26 AM
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Since OP was from England and now that some of the sting of the situation has worn off, I can now cut him some "extra" slack.

Some old British cars were actually reverse ground. Early Jag's were like this and I'm sure they weren't alone. In this case positive terminal does go to the chassis. Perhaps he has a collection of Jag's and had a momentary lapse when connecting the battery. (IMG:style_emoticons/default/beerchug.gif) Cheers Mate!

(IMG:style_emoticons/default/happy11.gif) The Lucas - Prince of Darkness moniker didn't come without justification.
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falcor75
post Jan 14 2020, 06:48 AM
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QUOTE(Superhawk996 @ Jan 14 2020, 01:26 PM) *

Since OP was from England and now that some of the sting of the situation has worn off, I can now cut him some "extra" slack.

Some old British cars were actually reverse ground. Early Jag's were like this and I'm sure they weren't alone. In this case positive terminal does go to the chassis. Perhaps he has a collection of Jag's and had a momentary lapse when connecting the battery. (IMG:style_emoticons/default/beerchug.gif) Cheers Mate!

(IMG:style_emoticons/default/happy11.gif) The Lucas - Prince of Darkness moniker didn't come without justification.


I wrote this for a friend a few years back when he got his first Jaguar... (IMG:style_emoticons/default/biggrin.gif)

Our Father Lucas who arth in Hell,
condemned by thy name.
Your darkness will come,
your shortcurcuit unfound,
positive earth as standard.
Give us today our burning harness,
and forgive us our use of heatshrink,
as we forgive those that use fuses.
Lead us not into electronics
but deliver us from logic.
For the darkness,
the nonexistant spark and the mysterious smoke are yours.
Now and intermittently.

Ohm.
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ctc911ctc
post Jan 14 2020, 07:38 AM
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Cannot resist..........

Years ago I met an older gentleman who's last name was "Lucas". He said that he had just retired (sold) a few auto dealerships in the northern SF area specialized in English cars.

I said that he must be tired of hearing the Lucas Joke. He stated that he had never heard it. So I told him....

Why do the English drink warm beer?

Because Lucas makes refrigerators too!

He was not amused, a friendship was not made.....

CTC911CTC



QUOTE(falcor75 @ Jan 14 2020, 07:48 AM) *

QUOTE(Superhawk996 @ Jan 14 2020, 01:26 PM) *

Since OP was from England and now that some of the sting of the situation has worn off, I can now cut him some "extra" slack.

Some old British cars were actually reverse ground. Early Jag's were like this and I'm sure they weren't alone. In this case positive terminal does go to the chassis. Perhaps he has a collection of Jag's and had a momentary lapse when connecting the battery. (IMG:style_emoticons/default/beerchug.gif) Cheers Mate!

(IMG:style_emoticons/default/happy11.gif) The Lucas - Prince of Darkness moniker didn't come without justification.


I wrote this for a friend a few years back when he got his first Jaguar... (IMG:style_emoticons/default/biggrin.gif)

Our Father Lucas who arth in Hell,
condemned by thy name.
Your darkness will come,
your shortcurcuit unfound,
positive earth as standard.
Give us today our burning harness,
and forgive us our use of heatshrink,
as we forgive those that use fuses.
Lead us not into electronics
but deliver us from logic.
For the darkness,
the nonexistant spark and the mysterious smoke are yours.
Now and intermittently.

Ohm.

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dt4
post Jan 14 2020, 01:48 PM
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QUOTE(Superhawk996 @ Jan 14 2020, 12:26 PM) *

Since OP was from England and now that some of the sting of the situation has worn off, I can now cut him some "extra" slack.

Some old British cars were actually reverse ground. Early Jag's were like this and I'm sure they weren't alone. In this case positive terminal does go to the chassis. Perhaps he has a collection of Jag's and had a momentary lapse when connecting the battery. (IMG:style_emoticons/default/beerchug.gif) Cheers Mate!

(IMG:style_emoticons/default/happy11.gif) The Lucas - Prince of Darkness moniker didn't come without justification.


thanks Superhawk but no slack is deserved in this instance
It was a monumental moment of fuckupery
I have had the battery off and on a dozen times, have 20 years of restoration experience and 35 years of diy mechanics so have no excuse.
I bet I dont do it again
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KELTY360
post Jan 14 2020, 03:28 PM
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The English language evolves through creative combinations of words in common usage. You sir, have skillfully woven such an example that should become a permanent part of the lexicon: fuckupery!

I can see the scene at a spelling bee clearly: Fuckupery - F-U-C-K-U-P-E-R-Y - Fuckupery.

Or better yet, the contestant asks, “Can you use it in a sentence?”

Classic! (IMG:style_emoticons/default/beer.gif)
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dt4
post Jan 15 2020, 01:12 AM
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QUOTE(KELTY360 @ Jan 14 2020, 09:28 PM) *

The English language evolves through creative combinations of words in common usage. You sir, have skillfully woven such an example that should become a permanent part of the lexicon: fuckupery!

I can see the scene at a spelling bee clearly: Fuckupery - F-U-C-K-U-P-E-R-Y - Fuckupery.

Or better yet, the contestant asks, “Can you use it in a sentence?”

Classic! (IMG:style_emoticons/default/beer.gif)


thanks Kelty
it looks like you reside in Townsend?
that's my surname (IMG:style_emoticons/default/smile.gif)
how about that !!
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