I need some help here. My volt gauge is reading below 13 volts, it dies if I disconnect the battery cable and it cranks like a low battery. I figured a bad alternator, I put a good one off my truck on and the same thing. I took them both to 2 different places and they both tested good. both charge fine on my truck. Is there a fusible link or something I should check ? BTW it's a 90 RS, 305 TBI.

 

with the engine runnning put a screwdriver or other solid steel item near the backside of the alternator in the center where the shaft bearing are in it and see if it magnetically sticks to the alt

if not then make sure the alt is wired right and connected to battery source

make sure test light glows at both red wires on the alt if not then make them be hot all the time, do what you have to

alot of the times i just loop the spade red wire down to the threaded charging post so they are both hot this way

the fuseable link at the starter that feeds one of the two red wires at the alt could be bad yes


good luck

 

also check fuseable links by the battery . happened to me . good luck .

UNCLE TOM