Normally you just connect it after the ignition key. That way, it'll turn off when ignition is off. I guess there will be a fuse for the ignition, so you don't need to install that either. Check out the MC28 schematic in the members section for a suitable place to tap the voltage.

For testing purposes, connect it directly to the battery via an inline fuse, like this.


You could then use the fuse as a switch. This way you can check the batt. voltage before and after, you turn on the ignition.

Later when problems are solved install the voltmeter as described on top.
_________________
Poul
"If Life Gets Boring, Risk It!"
MC21SE, KISS box
MC21SP, HRC box, racing loom