Charging system issue

[ray_mcavoy]

Assuming you have a stock replacement "3-wire" alternator and not one of those "1-wire" jobs ...

Check the voltage at the #1 terminal (usually has a "1" cast into the case next to it and the wire is usually brown). Should have power with the key on and/or engine running. If it doesn't have power with the ignition on the alternator won't charge. Check for a bad/loose connection on this wire where it plugs into the alternator and where it goes through the bulkhead connector on the firewall behind the fuse box. Also, if your truck has warning lights instead of factory gagues, this circuit is wired through the "GEN" light so a burned out bulb could be keeping the alternator from charging.