Hi,I have a 1975 F-250 4X4 Hi-Boy w/390 motor,can some one tell me the proper wiring from my alternator to amp guage? Thank you for all your help 390man

 

I would use a voltmeter instead for two reasons. It gives a better indication of what your charging system is doing, the ammeter will normally hardly move. It is a lot easier to hook up.

To hookup the ammeter you have to separate the alternator output terminal and connect one side of the ammeter to the alternator output and the main supply wire for the truck. The other terminal of the ammeter goes to the start solinoid + term.

Now when you start the engine, the ammeter will show a slight charge current into the battery. If the alternator fails, the ammeter will read negative as the battery is supplying current to run the truck. Also you need to run heavy wires into the cab which should be fused. A voltmeter is just a lot easier, Just one wire to a point that is hot with the ignition on.