Voltage to ground?

[empersons]

I am trying to diagnose an electrical short in my car, I assume its a short anyway. With the positive cable connected to the battery and the negative disconnected, I measure the volts between the negative on the battery and the cars ground and get 12.3 volts, give or take a tenth. I assume it should be zero unless there is a short somewhere.
Anyone understand electrical that can help me with this?

[71Corolla]

It won't be zero unless absolutely nothing is drawing power. For example the clock and the stereo are always drawing power, so there is a completed circuit and you will get a ~12volt reading.

[white90dx]

Sounds like a misunderstanding to me.

If the battery ground and the car aren't electrically connected, then they won't be at the same voltage. In this case, the battery is doing its job and keeps the negative terminal 12.3V below the positive terminal (really, it should be closer to 12.6V - your battery may be low or not being charged). Everything else in the car is sitting at the positive battery voltage because there is no way for current to get back to the negative battery terminal, and thus it stays at the positive battery voltage.

-Charlie