No power? Headlights still work though?

Hey guy I went to start my 2600i and when I did everything turned on for a second and then all my interior stuff turned off beside gauge cluster lights. Prior to this happening I drove to my gf's house just fine.now when I try to start nothing happens. I Sheba a aftermarket cig lighter that has a led light on it which usually shows power when I turn the key to on position and now when I do the light turns on for a second them dies off. Tried jumping it as no difference. And checked all fuses in cab there fine. And in engine bay There fine.

Look at the ECU circuit board behind the passenger kick panel for corrosion or it may be your ignition switch since it doesn't turn over.

Ok I'll look into. Thanks. How could I testy ignition switch?

Bypass the ignition switch by shorting the starter directly to see if it turns over.

Did you check your 80Amp main fuse? Actually remove it, clean contacts, I had a bad contact once, would do what you describe, the 80Amp fuse is screwed into the fuse box, and requres removal of the box under the hood. The 80Amp fuse supplies power to most of the truck, with the exception of interior light, headlights, and horn for the most part.

Can you show a pic where it's located plz?

Located just rearward of the battery, in the engine compartment. The large fuse must be unscrewed from underneath.

If the main was bad, nothing would get power.

Could it be a bad ground or power cable what else could it be?

Ok so weird thing I found going on here. There's a red "positive" cable coming straight of the battery terminal going into the cab. I bought the truck like this from a guy so I'm guessing there's some crappy wiring that he did that I'm finding now. The red "positive" cable burnt up a few months ago from me trying to start the truck so many times because it wouldn't start and I never messed with it after it did that. It drove fine and everything was normal except that when I turned my truck completely off now my heater and new cig lighter I put in turned off with th truck before my heater could turn on with or without the key on. Now I hooked that wire back up to the positive terminal for shins and gigs and now my truck starts and runs. If I disconnect it the truck does immediately. I'm confused as all hell here and I'm goin to try and follow that red cable tomorrow. Any ideas on what this setup is or where it could be going and my starter doesn't work when I try to start it but when I use this other push start button they installed it starts...