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Okay, so I wired it into the driving light harness, specifically, the same wires that go to the switch in my dash. It works, but it doesn't read full voltage. I verified this by slapping my multimeter on the battery itself and comparing the two. Is the voltmeter running low because I tapped into the switch wires that go through the relay? Does that reduce voltage?




Technically anything between the voltage source and the test point is a resistance and will lower the voltage... that includes wire (no such thing as a perfect conductor) however you're also comparing one meter to another. First thing you need to do is hook the LED volt meter up to the battery directly so compare a reading from there to a reading from the driving light point.

As to where it should be wired to, the correct place is to the fuse box, on the fused side, with its own (light gauge) wire.. You could tap into the parking light wiring, but your reading will be subject to any losses caused by tail light, parking light, and instrument lights and it means that if you ever use the park position on your ignition switch the volt meter will come to life too. The accessory socket connector would be great as there's nothing else on that circuit, except it's not switched. Personally I'd put it on the upper yoke with some double sided tape and run a light gauge wire directly to the back of the fuse box and hook it up to fuse #9 which feeds the starter relay, but at a point before any significant voltage drops. The meter'll pull next to no current so it'll have no real effect on the load on the fuse.

Matt Electronic mods for TBA/SM!