i have a 1979 Jeep Cherokee .i just recently changed my alternator due to falty bearings, i checked the voltage before i changed the alternator and it was reading 14.35,i replaced the belts before i went out to buy one. and it still was squealling so i replaced the alternator with a rebuilt one. and it only charged at 12.25 and it squealls very loudly. the battery was charged over night on a trickel charge and tested good, i adjusted the belts, but the tightest was the 12.25 reading. i took the ground wire off the battery and the squealling stoped but the reading from the alternator was 16.45. this is the second time i replaced it in two days with the same problem. my old alternator charged good but squealled, my two new alternators squeall and charged bad. could it just be two bad alternators? or a grounded wire?
If this happens to you, check to see if you have an external voltage regulator. The new alternator could have over loaded the old one and caused it to malfunction. I have run into a situation where I replaced a rebuilt electrical part twice and both were bad but that would be rare. Also check to see if the wires were connected correctly and that you don’t have any bare wires touching.