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Discussion Starter #1
I am getting lots of spark when connecting the negative terminal to a new battery in a friend's '87 Shelby Charger with a Turbo II. There was enough sparking to cook the edge of the battery terminal (see image below).



The ignition is off as well as any other draws like headlights, etc. He left it sitting for some time and this is a new battery. We also replaced the alternator harness since the old one had become hard and brittle.

I rechecked all the connections and can't seem to find anything that could be creating a draw, which is what I assume is causing the sparks. Any ideas?
 

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R.I.P Dennis Jarvis
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Is your ride stock or does it have extras like an MSD ignition etc
 

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You will only produce a large spark connecting the - cable if a circuit is alive.
With a draw like that the battery will be dead in a short time.
As stated above...
Are there any aftermarket accessories in the vehicle?
 

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Discussion Starter #4
You will only produce a large spark connecting the - cable if a circuit is alive.
With a draw like that the battery will be dead in a short time.
As stated above...
Are there any aftermarket accessories in the vehicle?
No MSD coil, car alarm, extra lights, stereo system or anything that would create this big of a draw. I'm stumped.
 

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90 Daytona Shelby, 89 Spirit ES, 96 Jeep XJ
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If it's heating up and blowing the fuse then you have a short to ground somewhere.

Same for the original poster, are the battery wires heating up at all? Maybe you created a short somewhere when you were replacing the alternator harness?
 

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the short has been there way b4 i took out the alt harness also.... all green an corroded in exposed area. fixing that now. but would that cuz the seat and door looks 2 stop workin?
 

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90 Daytona Shelby, 89 Spirit ES, 96 Jeep XJ
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A lot of the interior options on these cars share grounds (and fuses) with other systems. If you're blowing fuses then yes, other things would stop working.
 

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Discussion Starter #8
Back to my issue...could an ungrounded or cooked wire somewhere cause the sparking? I was not aware that issues like these could cause such a draw on the battery.
 

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I assume you did not leave the battery connected long enough to see if anything was running?
 

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Discussion Starter #10
I assume you did not leave the battery connected long enough to see if anything was running?
No. Is there a procedure to see what could be creating a large enough draw to spark the terminal? I would've thought one of the members familiar with charging system issues would have chimed in by now.
 

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This has nothing to do with "charging system issues".
Something in the vehicle is being powered on that should no be with the key off, possibly a relay stuck in the closed position.
Amperage flow is probably normal or a fuse/fusible link would have blown.
The only way to determine where the issue is will be to remove fuses one at a time and disconnect components one at a time until the arcing stops then you have isolated the circuit causing the problem.
 

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Discussion Starter #12
Haynes lists an even better procedure to find the short. Connect the postive cable to battery but instead of connecting the negative cable, ground a tester on the disconnected cable and touch the negative terminal. If it lights-up, you have a short.

Then disconnect the alternator harness (including the output line with the white connector). If the tester light goes out, it's a bad alternator. If the tester light stays on, then (and only then) should you start pulling fuses.

I did this procedure and found a wire going directly into one of the fuse slots. It apparently powered an amp. When I removed the wire, the light went out.

I have yet to reconnect the battery but I assume it will no longer have a large spark.

NOTE: Apparently on my car, when you open either door, the tester will light up so you need to pull fuses with the doors closed for an accurate reading.
 

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Maybe NAJ can shed some light on this, but I had the same problem in my 85 z turned out to be a diode under the hood, in the small harness that contains a ground to the head and also the wires to the speed sensor on the axle. This car is a real Frankenstein so I'm not sure if your car even has this diode or where it's located, but my 86 also has this as well as the spare harness I had from an 86. Might be worth a check
 

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Discussion Starter #14
Maybe NAJ can shed some light on this, but I had the same problem in my 85 z turned out to be a diode under the hood, in the small harness that contains a ground to the head and also the wires to the speed sensor on the axle.
Do you have a photo of this diode? The only ground I see attached to the head is the main ground from the battery/alternator harness.
 

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Sure looks like some kind of short to me. I'd start with pulling all fuses and see if it still does it. If it quits with all fuses removed put them back in one at a time till it does it again........
 

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Do you have a photo of this diode? The only ground I see attached to the head is the main ground from the battery/alternator harness.
I don't have a pic of it, but is on that harness you speak of. The diode is inside a length of heat shrink with I believe white wires and a brown wire (not positive, been awhile). Take the loom apart and carefully cut the tape apart. If it's there on your car, to test you need a hot wire from batt and a test light to make sure power only goes thru one way. On my car, it kept blowing a fuse and if I unhooked that ground on the head, the fuse did not blow.
 

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Discussion Starter #17
So it's located in the alternator harness? Following the Haynes procedure, I was able to detemine that the alternator and harness were not bad so it could not be this diode.
 

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I must have misread. This diode is in the harness that goes to the speed sensor and I believe the starter solenoid. Like I said though you may not have it on the newer car. Your car has the relay box on the driver side strut tower?
 

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Any arcing is caused by amperage flow, slight arcing is normal.
If you are getting excessive arcing when touching the - battery cable to ground or - post that means an electrical component in the system is powered on that should not be on or an electrical component or wire is shorted.

There is no simple way to single out exactly what is causing the problem.
You need to eliminate each circuit/system one at a time until the issue is gone.
1)Disconnect battery power from any installed aftermarket accessories.
2)Disconnect battery power from the alternator.
3)Run an IOD test.(Internal Off Draw)
a)Disconnect the + battery cable
b)Connect a digital multi-meter inline with the + battery post and + cable.
c)Be sure all doors are closed, no lights are on, all accessories are off and all controllers have gone to sleep (approx. 2 Minutes after meter connection).
d)Turn on the meter and set to Fused 10 Amp.
e)What is the amperage reading?
f)You should not be reading anymore than 30 milliamps (.030 Amps)
 
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