2000 GMC 1500 goes dead while hooking up trailer lights

Truck went dead while hooking up trailer lights. Electricity came back while in accessory positions. No blown fuses, 12 v tester shows fire everywhere (including relays). When I try to start it, nothing happens. Starter doesn't turn, solenoid doesn't click...nothing. Tried to hot start by touching the poles of the solenoid together. Heard a spinning or whizzing sound in the starter but shaft never would engage flywheel. What could be the problem?

Welcome to AF. Try tighening and cleaning the battery terminals and check the battery with a load tester.

Thanks for the response, but let me ask, If everything else electrical is working correctly, what would tightening the battery cables do? I mean everything was working fine. We had the ignition turned to accessory 2 while checking the trailer lights and all of a sudden, everything went dead. After a few seconds the headlights and dashboard panel lights came back but nothing from the starter. Matter of fact the only sound when ignition is turned to on position is clicking in the starter relay in the fuse panel. No fuses blown as I said before. I'm thinking perhaps we somehow fried the solenoid. Starter is hot according to 12 V tester, so I know there's fire coming from the battery since starter is connected directly to battery. I can't come up with anything else. Any suggestions would be greatly appreciated.

Bad grounds and connections can cause poor continuity when the load of cranking the engine is applied, see if you have 12v at the starter solenoid wire as you try and crank the engine.