How to measure -12?

[Zephyr]

hey guys when u got a circuit n want to measure the ground -12 how u measure it with a mulimeter/voltmeter thingy isnt it...BUT i want to know which wire is the ground in the car u c or 2 c if the ground is actually connected to a ground source...last time it wasnt n roasted my amp oopsie me aint playing with that wire again heh

edit:such as where do i stick the red n black sticks of the voltmeter?

 

[K10Daz]

Put the black wire to an earth i.e the body of the car (paint free) n put the red on the wire you wanna test! If you want to test a ground you place the black on an earth on the body of the car OR a wire you know is a definate earth an then place the red wire on the wire you wanna test, if no reading shows on the volt meter then its a ground, play about using batteries first to get the hang of it!

Hope this helps

Daz

 

[Andrew]

You should probably pick up a book about car electrics before you play about. Especially with wiring for ICE - the wire gauge is pretty large and means that really good fires can develop if it isn't fused correctly.

Just as a bit of advice - a reading of zero volts between ground and another wire does not indicate that the wire is also a ground - all it says is that there is no voltage there. It's also quite likely to be a switched positive.