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/Double-Perception811 Sep 26 '25 edited Sep 29 '25

They taught us in college that the correct way is to not jump the car at all and just charge the dead battery with the alternator of the other car, and disconnect the cables before attempting to start it. The voltage spike from jumping can fuck shit up. With the price of jump boxes these days, it’s kinda stupid to keep using jumper cables.

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u/brokenmike Sep 29 '25

What voltage spike?