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Something keep's killing battery which is new(battery) new starter. 2 alternator's . It's good at first start up then after heating up to normal and drive it for few min's ,will die off . battery will go dead. 92 150 4.9
Then connect the positive cable. Put a test light between the negative cable and the battery neg post. If the light lights up, you have a short. When you do the test, everything should be turned off, doors closed and if you have an underhood light remove the bulb.
If the light does light up, first, disconnect the alternator. If the light goes out, the short is in that circuit. If the light does not go out, one at a time, pull fuses. If when you pull a fuse the light goes out, you have found the problem circuit.
I would take a meter, and while it's running , check the battery voltage. It should be around 14 volts. If it's near 12 volts, the alternator is not charging. Since you have changed the alternator, I would suspect one of the fusible links to the alternator is bad. You can check this by taking the voltmeter, and put the negative meter lead on the negative of the battery. Put the + lead on the large output wire(s) on the back of the alternnator. You should get 12 volts. If you don't the fusible links in the output wires are burnt in two.