I accidentally put the positive on the negative while jumpstart

Tiny
MATTHEW MOORE2
  • MEMBER
  • 2003 CHEVROLET MONTE CARLO
  • 3.4L
  • 6 CYL
  • 100,000 MILES
I accidentally put the positive and the negative with the jumper box and now no dash lights come on or anything when I try to turn the key no response some people said it was the fusible links but I cannot locate them if that's even the problem I would appreciate any advice on this issue
Sunday, May 7th, 2017 AT 2:26 PM

5 Replies

Tiny
CARADIODOC
  • MECHANIC
  • 33,754 POSTS
Your car has dozens of computers that will be damaged by reverse polarity. To avoid that, they always have diodes built in. Diodes are one-way valves for electrical current flow. They are put in the computers backward between the 12-volt feed and ground terminals, so under normal conditions it's like they aren't even there. When you mix up the battery cables or jumper cables, the diodes become "forward biased", meaning they act like a short circuit. That is intentional and causes the fuse to blow, thereby protecting the rest of the computer.

You can be sure there are going to be multiple blown fuses. There will be a fuse box under the hood, and there should be one inside the car. Pulling each fuse out to do a visual inspection is very time-consuming. If you have a test light, the spade-type fuses have two test points on top that make the job go very quickly. Turn on the systems that are not working, then check for 12 volts on all of those fuses. If you find 12 volts on both test points, that fuse is good. If you find 0 volts on both sides, that circuit is turned off. You are looking for any fuse that has 12 volts on one test point and 0 volts on the other one. That fuse is blown.

Many older cars used fuse link wires spliced into the wiring harness. Those take some time to burn open, and usually will not do so from reverse polarity. Fuse link wires protect large circuits that feed multiple smaller circuits. It's the fuses in those smaller circuits that will blow and stop current flow.
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Sunday, May 7th, 2017 AT 4:37 PM
Tiny
MATTHEW MOORE2
  • MEMBER
  • 6 POSTS
Thank you for replying and I appreciate the helpful information but when I tried a new battery in it it worked fine and started right up
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Tuesday, May 9th, 2017 AT 5:12 AM
Tiny
MATTHEW MOORE2
  • MEMBER
  • 6 POSTS
Thank you for replying and I appreciate the helpful information but when I tried a new battery in it, it worked fine and started right up, thank god
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Tuesday, May 9th, 2017 AT 5:15 AM
Tiny
CARADIODOC
  • MECHANIC
  • 33,754 POSTS
Dandy. The cable clamps on jumper boxes and jumper cables make relatively poor connections and don't pass the high current needed to run a starter. They work by slowly recharging the car's battery over a period of a minute or two or three, so the battery can do the job. Those less-than-perfect connections make it hard for the accidentally-reversed polarity to overcome the battery's correct polarity, and that can stop the fuses from blowing, at least right away. Happy to hear you're ready to buzz off into the sunset.
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Tuesday, May 9th, 2017 AT 2:24 PM

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