Charging system problem please help!

[C203/4]

i have an 84 chevy pu i replaced alternator, battery, negative cable, and continuity of all wiring for the alternator the system has only 12.5 volts when it is checked with a voltmeter, you disconnect the positive cable and the cable read 14 volts hook it back up to the battery and it goes back to 12.5 and the system only runs off the battery. have replaced the batery twice, not it, replaced the alternator with three of them all test good. with the key off and the positive cable off a test light going to the cable and the positive side of the battery doesnt light up so no drain on the battery any ideas?

[ChevyTech]

Unplug the two wire connector to the alternator and make sure both wires have power to them with the key ON.

Does the alternator light work on your truck?

[piecesparts]

What was the reason for the change of the charging circuit items? Did you have a failure of the system prior to this changeout? If so, then you might look at a couple items.

#1 Look at the fusible link that is by the brake booster (between the engine and the booster against the firewall). If this is burnt or shorted, then the charging circuit will not work.

#2 Check to see if your electric choke wire is connected to the carb---If I remember right--this is the load for your alternator charging circuit use as a load trigger..