You can test the mag, 3 yellow wire Coming out of side of engine, follow them to the plug, you can unplug and set multi to AC then put 1 probe to ground the other in any hole,start engine check all three, should be around 70v and all should be very close to the same output. If that is ok, then you can check rectifier, but if nothing on dash and all wires hooked up I'd say you need a rectifier