Bad starter? Bad starter solenoid? Bad neutral switch?
Corroded, loose, or defective battery cables.
Check battery Check battery cables for corrosion or looseness Check fusable link
have you checked your cables, esp the ground?
If there is power lost, lights that dim and a battery light that comes on there is most likely a connection that is loose somewhere. It would be best to check the alternator or battery cables.
When key is on, is there power?(lights on the dash) If so, check starter/relay/solenoid. If not, check battery terminals, cables and fuses.
Any power in the battery? Bad cables, blown fuse or fusible link under the hood
Try looking at your fusible link that is connected to the battery, if it is 'blown' you will not get power to anything.
If the power goes off to everything when you hear the click it could be a corroded battery terminal. If lights just dim a little, it could be the starter or any of a number of other problems. If the lights dim a LOT, you might need a new battery. See if it starts when you connect jumper cables from a known good battery. If you haven't used jumber cables before, read and follow directions.
With a battery or solar power!
The battery ,which gives power to the truck, looses its power because the lights use power from the battery to work. It's just like a batery for a toy.
Voltage Regulator?
Check for: 1) dead battery 2) loose or corroded battery cables