don't use a test light either I recommend a real voltmeter so you can see full voltages there Link.
Does everything else in the truck work right now...
First thing to look at is fusible links under the hood. You may have a mains fuse block under the hood, check your owners manual and see, then put a voltmeter on each side of the fuses and check the voltages...without touching anything or probing as little as possible so as not to disturb something as it could be an intermittent that when touched starts working again.
Alot of times you'll find corrosion on a leg of a fuse or in the fuseblock itself.
If anyone goes have Mrs Link make that Chicken dish you won't be sorry
