Gen 1 charging issues?

While driving recently my headlights died and I got home and found the gen 1 light bulb was burnt out. I had the alternator tested and it is good. If I run the engine at high rpms the battery shows 14.5VDC. I also swapped the relays under the dash, but I still cannot figure out why the light is out and why my lights go dim driving at night.

Just the head lights? It seems your alternator is working properly so it is probably a light wiring or most likely. A light ground issue. Follow the steps in the -20 troubleshooting guide. Or, skip the step by step to just open the hood, find the ground bolt on the engine side of the valence for each headlight. Remove the bolt, attack the wire end and the valence with sand paper and put it back together. If that doesn't take care of it, go back to the -20 and test step by step.

I should have been more clear, the complete electrical system went. When I shut the truck off it wouldn't restart. The gen 1 light will come on every now and then (no rhyme or reason why, right before you crank the engine). Thanks for the input. I will look at the TM's

Wait, what condition are your batteries in? Have you tested them?