A few months ago I drove down to see my parents. It's a 200 mile trip. When I was within a quarter mile of the house my headlights completely cut-out. A few seconds later they began alternating between high beams (which I had on when it all started), daytime running lights and no headlights. It kept doing this rotation in an irregular fashion until I turned off my truck.

Any ideas? I'm stumped by this.

 

i'd bet a loose connection either on the headlight or the grounds. the flashing you were seeing was probably from loosing and regaining the connection. unless someone at one time had a weird police pkg setup

 

This could also be caused by a faulty headlight relay. I could easily see this happening if the standard headlight relay fails while the high beams are on. You would get a bit of a power struggle of sorts between the DRL's, the automatic headlights and the high beams.

The automatic headlights would try to kick on and fail because of the relay causing the no lights.
Then since the headlights are off the DRL's would try to kick on.
The DRL sensor then tells the regular lights to turn on because it is to dark out and to turn on the high beams because the switch is on for them.
The regular lights are supposed to come on with the high beams but don't because of the bad relay and the DRL's I believe are connected to detect the regular headlights not the high beams. So the DRL's pop on again.

A rather nasty cycle that must have been quite confusing for your poor truck's computer.

If you replace the faulty relay this problem shouldn't pop up again.

 

Same thing just happened to my son's 97 Blazer. I removed the headlight switch and opened up the switch assembly, cleaned up the contact point in the switch and it’s been fine ever since. Good Luck

 

I believe the true problem has revealed itself.

a few weeks ago I heard a clicking in my glovebox. the clicks were random but I noticed my DRL light flickering in concert with the noise. now two days ago my headlights and highbeams stop working altogether and only the daytime running lights work.

thinking it was strange I searched online and believe that the DRL relay behind my glovebox has gone bad, possibly in conjunction with the headlight switch. sooo...

guess I'll be ordering these in the next few days.
I'll update if that fixes the problem.

 

Let us know how that goes.