Hello. Truck is dodge 2500 cummins deisel 1999.

Wouldn't start the other day after sitting for a couple of weeks.

Testing said the alternator was done.

I installed remanufactured alternator.

Now the alternator is fluctuating from 12v to 14.5v when first starting the vehicle. I can hear the engine loading down when this happens. It does this for 5 -10 minutes then everything looks good. Also when first starting the vehicle voltage is down to 10.5v and then crawls back up to 14v then starts to fluctuate.
Is something causing the engine to load up or go on/off causing this?

The 2 batteries are old but i dont want to change them yet.

Hoping to find out the problem to fix it myself or i will take to auto shop next.

Thanks.

 

That is the grid heaters for the fuel totally normal...