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Well, I'm guessing you're not working on a Ford tractor, since no '60s Ford had an ammeter with the six-volt, positive-ground electrical system (unless someone removed a gauge and replaced it with an ammeter...all Fords from '58 to '64 had generator warning lights). So I'll include a '55-'57 Ford wiring diagram...it should be a BASIC diagram for just about any six-volt positive-ground tractor:
If you mean a test light when you say "12-volt tester", then yeah, it'll work...but the light will be dim at best. If you can use a multimeter, so much the better.
And yes...you need a 12V ammeter for a 12V system. 6V ammeter won't work right.
Rezvani's Latest Post-Apocalytic Monster Is a Ford F-150 Raptor Underneath
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