Disconnecting battery to work on electrical system

[Uncle Yaris]

Originally Posted by goku87

Does it really matter which terminal you disconnect whenever you are installing stuff? I've always disconnected the + but only recently for some reason I keep noticing everywhere that you should disconnect the -? Does it really matter?

Yes, it matters. If you disconnect the positive and accidentally short the wrench to ground, it can cause a fire or even an explosion (hydrogen gas in the battery - remember the Hindenburg?)

If you disconnect the negative, shorting to ground with the wrench won't do anything, since it's already connected to ground.