Both old and new alternator overcharging

[motor_head]

My FICM was bad in my late built 04, so I replaced it. Before I even started the engine after replacing the FICM, I upgraded the charging system. I installed a new 230 amp alternator and at the same time installed new Odyssey batteries. After the repairs, I started the engine and checked the voltage and it climbs upward to around 17.5 volts. I shut the truck down because it looked like the voltage still wanted to keep climbing. I started the truck again, voltage was at 14.2 and climbed upwards to close to 18 volts within 60 seconds. The old alternator was also overcharging. I'm going to throw my old batteries back in which were only a year old and tested good when I removed them. I just want to upgrade to stronger batteries than the 750cca that was in the truck when I bought it. I'm also going to reinstalling the old alternator until I figure this issue out. I'd appreciate any help. Thanks.

 

[lenzhotrod]

The first place to start is cleaning all battery and ground connections.