I would hook the black wire from alt back to the bulkhead & disconnect the bypass (from alt to battery or relay). this will let the ammeter read honest since you dont have a meter so we can easily tell when it we get it charging then you can reinstall the bypass if desired. do you have a 1157 dual filament taillight bulb & socket & pigtails handy in your parts pile that you could use to check if the blue wire ign1 circuit is hot at the alt and reg with key on? then when solved you can reinstall the 100 amp alt if desired (I hear it is a pretty trouble free unit). As said a ten dollar HF multimeter will suffice & if you buy something else, their coupons might let you have it for free