so i am having a strange voltage issue. i changed the battery, just got a new alt from mazda. tested the alt. wire and it is making connection. the car has fairly low miles and the wiring all looks good. here is the issue. i first installed the alternator it read 14.5 volts once i started it. about 30 seconds later it dropped down to 11.5 volts and keeps slowly dropping. now once i start it the alternator is just throwing out 11.5 volts. when the car is off the volts jump back up to 12.1 or more. i checked the belt and re tightened the alternator bolt. any ideas would be great. also this is the 2nd alternator it has done the same conditions to so i dont believe the alternator is to blame at this point.