The biggest load I think you would see is with the dash AC on,(the fan) and the electric condenser fans on in front of the radiator. Both on with the ac clutch might be over 50 amps. The fuel pump inside the gas tank, ignition, lighting, radio, wipers, dash lights. That puts a lot of load on that small alternator pulley with maintain the batteries too. The way to actually see if the belt is slipping on the alternator, see if that pulley will boil spit. It gets really hot when it slips. Check it right after you shut the motor off. if it was hot, you may have to change that serpentine belt, likely it's cracked and dried out. My 89 had the curved bracket with a slot the alternator bolt used to adjust the belt, I used a 2' long 3/8 extension to pry the belt tight. Since yours doesn't have smog pump, don't really worry about the belt being too tight. Just tight enough to prevent any slipping. if it had a smog pump in line driven by that belt, you would have to be more careful about the tension.