not charging on 1990 Dodge Ramcharger

i have replaced the alternator new battery and the voltage regulater and it is still discharging this is a 1984 model.i had the old alternator checked and it tested ok but i replaced it anyway.when i turn on the lights and heater the amp meter goes to discharge.Ihave checked for broken wires and not found any .this really has me stumped.

Asked by for the 1990 Dodge Ramcharger
did you check the voltage to the back of the alt? it must be 12 volts all the time.
i would start there.

no i have not. what kind of tester do i need for checking that?
a volt meter. you need 12 volts to the big fat wire on the back of the alternator.