voltage starts at 14 every morning but then drops below 12 shortly after driving

Question

Just bought a 1998 Nissan Frontier. It has a new alternator. For a while I was getting shorts at the terminal connectors so I replaced both. That seemed to fix the short but then I started having trouble cranking up in the morning because the voltage of the battery wasn't quite there. Then suddenly it wouldn't crank at all, just turn on the electronics and make a clicking noise.

After jumping the battery things were back to normal but the voltage will still drop when driving or after letting the car idle for a few minutes.

Since it's a new alternator and battery, could it just be a connection issue? If so why does it always start out at 14 volts every morning when I crank it?

Could one of the electronic components cause this? The guy that had it before tried to put a stereo in but I disconnected most of that (except what I believe is the antenna ground). Car seems to maintain voltage for much longer when A/C, Radio, and lights are off, but it still drops after a while of driving.

Could it be that my vehicle just operates at closer to 11 volts? Is that normal?

Answer 1

I was thinking at first maybe it was the regulator which is sometimes found in the ecm. After looking at the service manual I see that for the 98 its built into the alternator on this one. Still possible the one you bought is bad which I hear happens quite often on starters and alternators but I would rule out everything else before considering it defective. Check your connections not just at the battery posts but at the cables going into the terminals. If it was in very bad shape before you may even need to cut some of the old wire back to find some that is better conducting and not so oxidized. Make sure to check the fuse/fusible link to make sure they are ok. 11V is not normal you either have a issue with the regulator, battery, poor connections or short somewhere that is bringing it down.

Diagrams are from Nissan service manual, 1998 Frontier.