Lucky Break -- Hopefully -- After a Jumper Cable Mishap

Dear Car Talk: Several weeks ago, I was waiting in a parking lot and I was asked if I had any jumper cables. I did. The guy who asked said an approaching pickup truck offered him a jump but didn't have cables. While the pickup was being positioned, I attached the cables to the dead car's battery -- properly (red to positive, black to negative).

When Pickup Driver took the other end of the cables, I said, "Be sure to put the red clamp on the positive terminal." He retorted, "I know what I'm doing!" Well, he didn't. When he put them on, the red clamp on the dead car literally fried, melted part of it and popped off -- he had reversed them.

He got really irate when I told him he had them on the wrong terminals, instead of owning up to his mistake. When he did put them on the correct terminals (I checked), I was able to put the damaged clamp back onto the positive terminal of the dead car's battery, and the car started.

The owner of the dead car volunteered to buy me new jumper cables, which I refused. But it left me curious. So far as I could tell, the only damage was to the cable clamp on my jumpers. It was minor enough that when I got home, I fixed it with my Dremel, and it's still very usable.

But did that mistake likely cause any damage to either the dead car or the pickup? If so, which one was likely damaged? -- Cary

Either one could have been damaged, Cary, but it sounds like neither one was (sorry, I know you were rooting for the pickup to be fried).

My guess is that the spark that occurred when the pickup guy hooked up the final wrong cable blew the clamp off the battery before any electronics could be damaged. Of course, that's a guess on my part. For all I know, the pickup truck driver may be setting his seat heaters to "char" every time he turns on his windshield wipers now. And the other guy's AM radio may be coming through his heater vents.

While it's certainly possible that electronic damage can show up later if an electronic module was damaged, it often reveals itself right away. So, I'm going to remain hopeful that your jumper cables were the only victims here.

Had the cable remained on there even a little longer, there are plenty of electronics that are sensitive to voltage surges. Most modern cars now have 30, 40 or 50 computer modules that have a hand in everything from engine management to power windows. That's where the damage would be found.

But I think you all got a lucky break, Cary. Pass along our get-well-soon wishes to your jumper cables.


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