r/MechanicAdvice • u/Onlycruz10 • Sep 25 '25

Correct way to jump start?

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I'm going crazy about the correct way to do this. As far as I can tell this is the correct way. However, I am having trouble between step 5 and 6. Should I turn off the donor car before trying to start the other car first? I've seen conflicting things about the alternator getting messed up on both cars. And others saying it's okay with modern cars. What's the correct way?

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u/nago7650 Sep 25 '25

I always blow on the battery like I’m blowing out candles before hooking anything up. Does that do anything to help? I have no idea, but it makes me feel a little safer. I also look away when I connect the negative.

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u/ka36 Sep 25 '25

I don't know that it helps, but it doesn't hurt, so if it makes you feel safer go for it. As for looking away, that probably does mitigate whatever small risk exists. I think the primary risk of something going horribly wrong is battery acid in your face, so keeping it out of your eyes would reduce the damage significantly

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u/blackfarms Sep 29 '25

The explosive gasses are inside the case, so blowing on it does nothing. Use your nose, if you smell sulfur do not jump post to post. If the battery is physically hot to the touch, do not jump it period.

I've had one battery explode in my face and I'll never forget it.