Battery installed backwards

Tiny
JOSEPH RUIZ2
  • MEMBER
  • 2003 KIA OPTIMA
  • 98,000 MILES
I put on my battery backwards and I made a spark. Did not do anything yet need to get a proper battery tomorrow. Will the car turn on when I get proper battery? What was the spark from?
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Monday, June 19th, 2017 AT 8:58 PM

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Tiny
CARADIODOC
  • EXPERT
There are going to be numerous blown fuses, I hope. Electronic circuitry cannot tolerate or work with reverse polarity. To reduce the potential damage, all computers have "diodes" built into them to protect them. A diode is a one-way valve for electrical current flow. They are installed in computers backward so it is like they are not even there. When the battery or jumper cables are connected backward, the diodes become "forward biased", meaning they act like a short circuit. That short causes the fuse to blow, then there is no further current flow to do any damage.

Ninety nine percent of the time the blown fuse is the only thing that needs to be replaced, but there are times when the diode melts inside and becomes totally shorted. When that happens, the fuse will blow again, either right away, or when the ignition switch is turned on.

To prevent this from happening again, there is always a plus and minus sign next to each battery post. The negative cable has a fat cable that bolts to the engine and a smaller wire that bolts to the body. The positive cable goes to the starter motor, and on newer vehicles, a smaller wire that bolts to the under-hood fuse box. When there is still some confusion, observe that the positive post and cable are larger in diameter than the negative post and cable.

We used to be able to find which was the positive cable by its red insulation, but that is not always the case today. Negative cables used to be black, but a few are bare cables or bare braided straps. Some batteries have red paint spots on the positive post and green paint spots on the negative post.
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Monday, June 19th, 2017 AT 9:49 PM

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