Dear Tom and Ray:
Why do I keep hearing that you should never allow two vehicles to touch while jump-starting one of the vehicles? I recently e-mailed a local radio-show host here in my area who does an auto-repair show on Tuesday evenings, but even he admitted that he had heard this but had never checked it out and, therefore, couldn't answer my question. Do you know? -- Brian
TOM: I would assume that's from the days when cars had exposed metal bumpers.
RAY: Cars still have metal bumpers, but they're now encased in rubber or plastic. But if you had two cars with exposed metal bumpers, AND the cars were touching, AND you hooked up a jumper cable incorrectly, attaching the positive of one car to the negative of the other, then you could possibly cause an explosion. You'd be, in effect, shorting out the battery in the car that was attached to the positive terminal, and it could blow up on you.
TOM: But it's largely irrelevant today, Brian. Unless you happen to have one of those few pickup trucks or SUVs that are still sold with chrome bumpers, and you're being jumped by another one, it's just not an issue.
RAY: Right. Nowadays, all modern cars can have their bumpers touching. They can hold hands, kiss, do whatever they want. As far as we're concerned, what they do while jump-starting in the privacy of their own driveway is none of anyone else's business.