2G Galant 90A alternator issues

[Steven A Schiltz]

Hey y'all I got a wiring problem. My eclipse alternator took a shit so decided to upgrade to the galant 90 amp ( I have a 98 gsx) and when I first start up the car it'll charge at 13.8 to 14.2 volts but noticed( with my voltage gauge in the car) it would drop to around 12.5 volts but would unplug the connector to it and it would read 14.6 volts then plug it back in and it would read 13.8 and stay charging untill I shut the car off and would do the same thing when I'd restart the car. Either cold start or warm. So the next day I decided to put a multi meter in line to see if my voltage gauge was off. So here what I found on first start would charge 13.8-14.2 volts for about 2-5 mins. Then notice it would drop to 12.6 and slowly drop. Unplugged the alternator and would read at 14.8 volts and let it sit there for a few unplugged and plugged it back in and would read 13.8-14.1 volts and let it sit there and run for a bit and watched the meter and no drop found on the way home I watched the voltage on evoscan and it stayed around 13.8-14.1 volts the whole way (about a 30 min drive) and IV read the galant alternator is a drop and plug and play type thing is there something I'm missing here to cause this?