Voltage Gauge

[Jim-ME]

I was given a Smiths voltage gauge and I'm not sure how to wire it in. It has 2 terminals on the back, one with a yellow and black wire attached to it and one with no wires attached. FWIW the face has no numbers just a normal range with white either side of the normal slot. On the back there is one terminal with either the #1 or - stamped in the housing and the other terminal is marked #2. The first terminal #1 or - has a yellow and black wire attached while the #2 terminal has no wires attached. I would like to test it before I mount it. Any help would be appreciated.
Jim
PS
If this is is of any help there is a label with 073 on it.

[NickDawson]

I just went and looked at mine, it has numbers so must not be a smiths.. but it also has two leads. One grounds out, the other runs through a distribution block in the hood...presumeably to ingnition triggered fuse or terminal (didn't have me multimeter to check it)... i think its pretty simple.

Isn't yellow gnd in the lucas world?

[navydevildoc]

Not sure of your exact gauge, but one side of it needs to go to ground, and the other side needs to go to switched voltage from the ignition. If it's a "stock-ish" harness, then look for either white or green wires to provide 12 volts switched, and black for ground, or you could fashion your own ground wire to the back of the dash panel somewhere. If you need a new ignition switched feed as well, the "I" or "IG" terminal on the back of the ignition switch (on a II or IIa) gives you that.

If you want to test the reading first, then simply connect one terminal to the ground on the battery, and the other to the positive. Should jump to life. If it goes "backwards", then just reverse the leads on the back.

[Jim-ME]

Hooked it up to my booster pack and that did the trick. It reads perfectly. Still wonder what the additional wire is for.
Jim