The proper jump start procedure...

Dear Car Talk

Dear Car Talk | Nov 01, 1989

Dear Tom and Ray:

A friend needed a jump start the other day. He attached the last negative cable to his negative battery terminal. I said he should have attached it to a metal surface other than the battery. Who was correct?

RAY: You are correct, John. But let's go through the entire process since jump start season is upon us.

TOM: According to the Geneva Convention the red cable is used for positive and the black for negative. So first hook a red clip to the positive terminal of the dead battery. Next, hook the other red clip to the positive terminal of the good battery with the engine of that car running.

RAY: Then stand around and rub your hands together for a few minutes. When you can move them again, attach one end of the black cable to the negative terminal of the dead battery. Then clip the other end of the black cable to a non-moving, metal surface in the other car. Don't attach it to the battery, and don't try to hook it to a moving fan blade like my brother always does. Hook it to a substantial piece of the engine or frame.

TOM: The reason you want to avoid the final negative terminal is because if you have hooked up the cables incorrectly, there will be sparks, but at least they won't be in the vicinity of the battery. Sparks could ignite hydrogen gas which can escape from batteries. That's also the reason you hook up the good battery last. Since it's not dead, it's less likely to be leaking hydrogen gas.

RAY: The reason you want the engine of the "good" car running when you hook up the cables is that the dead battery will start draining current immediately. If you hook the cars up while their both turned off, you may find the "good" car hard to start when you're ready to go.

TOM: For those of you who either don't carry jumper cables, are intimidated by large amounts of electricity, or are not absolutely certain which terminal is positive and which is negative, we suggest you call road service and walk to your favorite Italian restaurant. Order a seven course meal, and by the time you get to the espresso and antacids, the tow truck should be there ready to help get you on your way.

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