Doc, head down to local auto parts store, either buy one or see if you can rent it(multi-meter). To use it, flip it on, then have wife, son, daughter, annoying neighbor..anyone, help you.
Locate the relay,..where the 2 big red cables enter a black box, and attach to inside, that your relay. The cable from battery to relay, should read 12-ish, the other post wont have a reading until someone hits the "start/stop" button.
On the multi-meter, you have a blck and red wire leads. Connect/touch the red lead to the post, and the black to a good ground...battery, expose metal,.ettc. All there is bud.:cheers: