Digital Voltage Meter

[mymonstertruck]

You don't need a switch. Just use the main negative wire you ran to the batteries as you main negative. Then run your hot wire from the meter to the back of the key switch. They key switch has a 48volts on it. So when you turn the key on the meter will light up. You can use a volt meter to test the post on the back side of the key switch for the 48 volts. Very simple so the meter will only come on when the key is on.