2007 Chrysler Town and Country Installed battery backwards?

  • 6 CYL
  • FWD
  • 27,000 MILES
I bought a replacement (used) battery for a Chrysler Town and Country. I got it from my father who can't drive any longer and am just planning on selling it. I am not familiar with the car and in installing the battery may have gotten it in backwards. I connected what I thought was the positive terminal, then the negative terminal -- which sparked when I connected it.

Now there's no electrical power at all. I'm afraid I got the battery in backwards and fried something expensive. Either that or the new battery is dead. Does this car have protection against numskulls like myself like a fusible link or a master fuse? I wanted to check before I tried reversing the battery and re-connecting it.
Do you
have the same problem?
Saturday, January 23rd, 2010 AT 9:08 PM

1 Reply

The worst thing you can possibly do is to connect it the other way. That will guarantee that you had it backwards at least once.

The positive battery post and cable are larger diameter than the negative post and cable. The battery posts are marked with plus and minus signs, and the positive cable is red, the negative is black. You should always connect the positive cable first. Its sloppy fit is the clue you have the wrong battery post. By connecting the negative cable last, there will be no sparks if the wrench hits the body of the van. Even if you can't see the cable colors in darkness, the negative cable will always have one small wire that bolts to the body, usually on the inner fender or near the radiator.

The alternator has diodes that are one-way valves for electrical current. They are in the circuit backwards and prevent current flow, but when the battery is connected backwards, unlimited current will flow. Many vehicles now have large fuses just for the alternator. That fuse is designed to protect the wiring from overheating and melting. It might not blow fast enough to save the diodes. A blown alternator fuse and / or a defective alternator will not prevent the engine from starting or running but it will lead to a discharged battery after a couple of hours.

Computer modules usually have diodes installed backwards between their power and ground wires. The diodes don't allow any current flow until the battery is reversed. Then, they conduct very high current which should blow the fuse to protect the rest of the module. The fuse often doesn't blow fast enough and the module is permanently damaged.

The first thing to do is to check for blown fuses. It's not uncommon to see a small spark when the last battery cable is connected. This is from the current surge as computer memory circuits charge up. The surges have also been known to cause fuses to blow, but usually not more than two. If you don't find more than two blown fuses, there may be nothing wrong with the way the battery was connected. If you find a bunch of popped fuses, replace them one at a time as you get the various systems working. Some computer module might need to be reprogrammed at the dealership, but that is really a big GM trick.

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Tuesday, January 26th, 2010 AT 6:22 AM

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