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Did I damage my friend’s car when I jump-started it?

During the first cold snap of the year, a co-worker called asking for a jump-start. I pulled up beside her car in a crowded parking lot and put the cables on, When I tried to start my car she waved madly and we noticed smoke coming from the cables. I noticed I had put them on wrong – negative to positive on my car. I disconnected the cables, which were obviously damaged and drove her to work. Everything seemed to be working okay on my car. During the lunch hour, I bought a new set of cables and we jump-started her car. Everything was working okay there as well. When she got to work, she said the radio in her car was not working. The next day, she took it to the dealer who said there was a problem with the electrical system. Could I have caused that problem? – Brian in Calgary

You almost certainly did.

I am surprised the radio is the only thing damaged by the reverse current through the system. There are an amazing number of devices connected to the system that could and perhaps may have suffered damage.

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It is likely she has not discovered the other damage yet. There are circuit breakers or fuses that might have popped and prevented damage but it is likely you may be in for a major bill – hope your insurance covers it.

Hopefully that replacement set of cables you bought were the new-generation ones that won't allow an improper hookup.

Do you have an automotive maintenance or repair question? We can help. Send your queries to globedrive@globeandmail.com

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