2009 Chevy TrailBlazer - headlights not working?

[Woogeroo]

not my contraption, this one belongs to my pops:

2009 TrailBlazer - headlights out.

All of the other external lights work, flashers, blinkers, park lights, etc. Just no headlights.

He checked the headlight fuses under the hood and and replaced the headlight relay, no joy.

With my very limited knowledge about any car built in this century, I'm now thinkin' a wiring situation or the big ol' headlight switch.

Then again, I guess both bulbs *could have* suddenly gone out at exactly the same moment... but I doubt it.

I looked through the fuses under the passenger seat... they were all for the lights that are actually working.

A few of the labels tho', not really sure what some of the acronyms meant, maybe it's one of them?

Any ideas on other things to check?

Troubleshooting methods?

We have multi-meters and wires, electrical connectors...

Thanks folks.

-W