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914World.com _ 914World Garage _ battery connection screw up

Posted by: dt4 Jan 12 2020, 09:57 AM

I have had the battery off the car whilst stripping paint and priming etc.... but thought it would be good to turn the engine over and run it for a while to keep things in good health etc.....
I had the battery on the bench to charge it and then put it back in the car but very stupidly put the negative lead to positive terminal and positive lead to negative terminal.
I didnt turn the key as I was checking other things when I realised what I had done.
I noticed that there was a smell of smoke coming from the alternator area and the tin on top of the engine in that area was warm so suspect there is a connector to the alternator under there?

I put the terminals on the right way around and tried to start the engine but it appeared the battery had drained?

I recharged the battery overnight but wouldnt start, again the battery seemed low on charge
Apart from seemingly screwing the battery, is there other damage likely to have occured

cheers
David

Posted by: Superhawk996 Jan 12 2020, 12:04 PM

sad.gif

There is almost certainly other serious damage if you smelled smoke.

There is no simple answer. If you're not experienced at electrical troubleshooting or lacking for patience I would recommend that it go to an electrical specialty shop.

You don't mention if you have original fuel injection of if the vehicle has been switched to Carbs. At this point having Carbs would work in your favor since there is a possibility that the fuel injection ECU (amonst other things) just got fried.

If you have a schematic, patience, and some experience with electrical items, you'll just have to start tracing wires, checking for blown fuses, looking for blown relays, searching for burned wires, etc.

Posted by: wndsrfr Jan 12 2020, 12:32 PM

QUOTE(dt4 @ Jan 12 2020, 07:57 AM) *

I have had the battery off the car whilst stripping paint and priming etc.... but thought it would be good to turn the engine over and run it for a while to keep things in good health etc.....
I had the battery on the bench to charge it and then put it back in the car but very stupidly put the negative lead to positive terminal and positive lead to negative terminal.
I didnt turn the key as I was checking other things when I realised what I had done.
I noticed that there was a smell of smoke coming from the alternator area and the tin on top of the engine in that area was warm so suspect there is a connector to the alternator under there?

I put the terminals on the right way around and tried to start the engine but it appeared the battery had drained?

I recharged the battery overnight but wouldnt start, again the battery seemed low on charge
Apart from seemingly screwing the battery, is there other damage likely to have occured

cheers
David

I've been there, done that. It kills diodes and possibly more in the alternator... likely have to replace it... easy to do on a T4, PITA on my /6....

Posted by: dt4 Jan 12 2020, 12:42 PM

I'll start with a new battery and replacement alternator (when I find one) and take it from there
thanks for the replies

Posted by: Mark Henry Jan 12 2020, 01:50 PM

The radio is likely toast but most else on the dash end is OK I'd think.

I have OCD triple checking, then checking again when it comes to connecting batteries. Always the ground is the first off and last on connections.

Posted by: dt4 Jan 12 2020, 02:07 PM

Is it safe to put a new battery on the car and try it?
If the alternator is toast, what effect would trying to start it have?

Posted by: Superhawk996 Jan 12 2020, 02:32 PM

QUOTE(dt4 @ Jan 12 2020, 03:07 PM) *

Is it safe to put a new battery on the car and try it?
If the alternator is toast, what effect would trying to start it have?


I would not start by installing a new battery and hoping for best given that you smelled smoke.

You likely have shorted wiring now either from melting and possibly from diodes. When diodes fail they usually go open but I wouldn't risk it.

At least start by using an Digtital Multi Meter to see if the battery + is shorted to ground.

After that I wouldn't even consider attaching the battery until you've inspected all the engine harness wiring starting with the alternator and the ignition coil.

Posted by: SirAndy Jan 12 2020, 03:17 PM

QUOTE(Superhawk996 @ Jan 12 2020, 12:32 PM) *
I would not start by installing a new battery and hoping for best given that you smelled smoke.

You likely have shorted wiring now either from melting and possibly from diodes. When diodes fail they usually go open but I wouldn't risk it.

At least start by using an Digtital Multi Meter to see if the battery + is shorted to ground.

After that I wouldn't even consider attaching the battery until you've inspected all the engine harness wiring starting with the alternator and the ignition coil.

agree.gif

Don't put a battery back in there until you tested all wires ...
popcorn[1].gif

Posted by: SirAndy Jan 12 2020, 03:20 PM

QUOTE(SirAndy @ Jan 12 2020, 01:17 PM) *
Don't put a battery back in there until you tested all wires ...
popcorn[1].gif


You don't want to run current through something like this:

IPB Image

IPB Image

IPB Image

Posted by: dt4 Jan 13 2020, 01:25 AM

@http://www.914world.com/bbs2/index.php?showuser=179 @Superhawk96
Thanks for the pointers guys, I will heed your advice

Posted by: Breaker Jan 13 2020, 03:57 AM

Just one additional thought:

IF the alternator is new, and IF has never been used since it was installed, then it could be an issue with the + threaded stud touching the alternator tin. It's often too long, and this would short regardless of polarity.

Posted by: Chi-town Jan 13 2020, 10:41 AM

Do not install the new battery. Pull the alternator and check for damaged insulation on the primary wire.

Posted by: 914fahrer Jan 13 2020, 11:32 AM

I think You shot the diodes of the altenator.They resist this only a short time. sad.gif

Posted by: dt4 Jan 13 2020, 02:48 PM

QUOTE(Chi-town @ Jan 13 2020, 04:41 PM) *

Do not install the new battery. Pull the alternator and check for damaged insulation on the primary wire.


will do Dylan, things were going so well !!

thumb3d.gif

Posted by: dt4 Jan 13 2020, 02:49 PM

QUOTE(914fahrer @ Jan 13 2020, 05:32 PM) *

I think You shot the diodes of the altenator.They resist this only a short time. sad.gif


I have found some one close by that repairs alternators so I will get it over to him

Posted by: Chi-town Jan 13 2020, 06:47 PM

Ok, if you need an alternator or harness let me know and we'll get one shipped.

Posted by: KELTY360 Jan 13 2020, 08:13 PM

This is a great learning opportunity to get to know your multimeter. Spend time learning to test electrical functions. You’ll be better prepared the next time you let the smoke escape from the wires.

Posted by: DickSteinkamp Jan 13 2020, 10:13 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?

Posted by: bbrock Jan 13 2020, 10:26 PM

QUOTE(DickSteinkamp @ Jan 13 2020, 09:13 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?


The way I see it, any circuit that is switched and the switch was off when the battery was connected backward should be fine. Any circuit that is always energized is subject to damage. Modern radios often have a switched and unswitched circuit and of course, any radio can be wired either switched or not.

Posted by: dt4 Jan 14 2020, 02:54 AM

QUOTE(Chi-town @ Jan 14 2020, 12:47 AM) *

Ok, if you need an alternator or harness let me know and we'll get one shipped.

You are a diamond geezer (as they say in the South)
thanks Dylan, let me see how it tests out

cheers

Posted by: dt4 Jan 14 2020, 02:56 AM

No radio fitted at present so don't have that to worry about idea.gif

Posted by: Superhawk996 Jan 14 2020, 06:07 AM

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 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.

Posted by: Superhawk996 Jan 14 2020, 06:26 AM

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. beerchug.gif Cheers Mate!

happy11.gif The Lucas - Prince of Darkness moniker didn't come without justification.

Posted by: falcor75 Jan 14 2020, 06:48 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. beerchug.gif Cheers Mate!

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... 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.

Posted by: ctc911ctc Jan 14 2020, 07:38 AM

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. beerchug.gif Cheers Mate!

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... 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.


Posted by: dt4 Jan 14 2020, 01:48 PM

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. beerchug.gif Cheers Mate!

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

Posted by: KELTY360 Jan 14 2020, 03:28 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! beer.gif

Posted by: dt4 Jan 15 2020, 01:12 AM

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! beer.gif


thanks Kelty
it looks like you reside in Townsend?
that's my surname smile.gif
how about that !!

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