88 f250 electrical problems

[stacked87f250]

i got a 88 i just put a brand new alt. and batteries on and the batter light was on... did a voltage test it said 12.5 with fresh batteries... i tried a buddys alt. on my truck knowing his is good and still the same thing... input anyone?

[totalloser]

The batteries should be 12.6 full charge sitting with the truck off. The voltage should be at least 14 or so with the engine running. I say take a look at the connections first and foremost. Wire brush those suckers and make sure everything has a good connection.

If all is good, and the voltage comes above 12.6 when running, maybe it's the dummy light circuit at fault. ???