Pos is battery
Neg is battery neg (for light)
Third one is for sender.
As mentioned, get a voltmeter to go alon
Do you have a model number or anything? O need to know if it's a mechanical or electrical gauge It says you need an external electric source (ignition switch or headlights) to power it so I'm assuming that goes there I will send you the pdf I found
Its electrical for sure
Pos is to the battery, middle is to the neg on battey and the middle is to the sender.
