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today I've made a very stupid mistake when jumpstarting my friends car, which is a vw golf in diesel. His car started succesfully and I took off both cables from my battery, when I wanted to take off the cables from his battery the ends of the cables were hanging loose and they touched themselves for a very short time, I guess it could be around 1 second. Of course it started sparking, I disconnected them immediately. The engine was still running, he shut it off and it started again correctly. We drove off like nothing happened, but I'm very nervous that I could have damaged something in his car. Is it possible that something happened even though the car was working fine?

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Well, if it is charging and all is fine it sounds like you got away with it.

Don't try it again as you may not be so lucky...

It is possible to blow the alternator, or some of the other electrical components or even cause the battery to explode...

The "proper" method is to first remove the negative from the "dead" vehicle (the lead should not be on the negative terminal but on an engine mount or bracket) and then the negative from the "supply" vehicle. Then remove the positive from both - now the order does not matter so much.

  • I'm too afraid to ask him. There was no battery charging fault light on, would it pop up if the alternator was damaged? As for the electrical components, shouldn't the fuses protect them? – hazelnutek Aug 16 '18 at 11:12
  • Fuses won’t always protect from a surge of high voltage - fuses are designed to protect the system from a short circuit as caused by a wire being cut for example... Designing a perfect fool-proof system is hugely expensive and also based on risk frequency ie how often that situation is likely to occur... – Solar Mike Aug 16 '18 at 11:47

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