I have a 05 aveo. My thermostat housing blew apart and I fixed that all up. At the same time my battery light came on so I replaced the alt. Battery tested good at 709 CCA of 540. Now with new alt the battery light is off but the car runs at 12.5 volts. Is there anything I should check?

And I would like to add I am a ase tech and have checked voltage to alt and and voltage at the voltage regulator. Only thing I have not changed is the battery. This is driving me nuts cuz of the fact I have a 8 month pregnant gf driveing it