I'm still looking for simple tests for the gauges. I'll let you know what I come up with. I found one for the temp gauge but you'd need a 75ohm and 1400ohm resistor to do it. Can't find anything for the oil pressure gauge. The volt gauge should be as simple as applying voltage across the contacts. You could just put jumpers across a hot 12V battery and see what it reads. Should read about the same as a multi-meter.
I'm sure that the oil pressure is resistance based as well, but I have not found the ranges. I'll keep you posted man!
I'm sure that the oil pressure is resistance based as well, but I have not found the ranges. I'll keep you posted man!