I hope you’ve got your voltmeter working now. If not,you need to determine when you want it to work. I’m guessing since you mentioned the key switch that is where you will wire it. That’s what I’d do. Not familiar with the wiring on your buggy. I’d ;suggest you probe around with a voltmeter…oh wait…that’s what you have…probe around the wires on the key switch to figger out which wires are hot with the key in the on/run position and wire it there. Should be an easy task. Decide where you want it mounted and run two wires from that location to the key switch harness and hook them to the 2 wires you have found the proper voltage on. Wish I had a diagram and could point you to the right wires but that is the fun in doing it yourself. Good luck on the project and also in your quest for more info on the R/T issues…I’m working on a Hunter 4x4 and am having problems finding info as well. If I run across anything that will help you I’ll pass it along…don’t give up. Your speed issue could end up being a loose/broken/intermittent wire or connection.
Take care and much luck to you,
Mike
Oh Yeah…don’t rely on chassis ground as you would on an auto/truck. Most I’ve saw of these require a separate ground for each accessory device. You may end up connecting the meter to where the power inputs to your converter…