I discovered a feature I didn't know about yesterday. Although it's not documented in the manual, it appears that if you accidentally leave headlights on ("on", not "auto"), and walk away from the car, at some point they'll turn themselves off to save the battery.
I experimented a bit yesterday, and drove to work with lowbeams and highbeams on. I was trying to see if the heat build-up would do anything to clear the condensation in the (cracked) housing. Unfortunately, once I got to my parkade, I must have walked away with the lights left on. But 8 hours later, when I came back to the car, the lights were off, but the car started without a hiccup. They must have turned themselves off; even though the battery is fairly new, running it down like that all day surely would have killed it.
Has anyone else seen this?

 

my 06 ody does this. it's not new.
i think my 04 accord did it too.

 

My 2001 Acura TL does that, they turn off after about 15 seconds.

 

That's cool, I never knew that!

Just fyi...even if the heat does clear the condensation it will return immediately after you turn your lights off because the outside will cool much faster than the inside.

You're going to have to fill that crack (clear RTV sealant would work). Then remove the side marker and high beam bulbs and use a hairdryer and route the heated air in the side marker hole and out the high beam hole (for about 5 minutes). This will remove the humidity that's trapped inside.

*credit to rockstar143 for the hairdryer tip

 

if you leave them on; they will get killed in 15 secs like the previous poster said.

the cool thing with those that DONT have auto headlights; is that when you start the car, the head lights will be on!

 

Yeah...as I said in my original post, is was a bit of an experiment, though not one for which I held out much hope. The thought was that if I could vaporize the moisture, and if the inside of the housing heated up enough, there might be enough pressure to push some of that moisture back out through the crack. Winters here get pretty cold, so the ambient air is pretty dry, so I wondered if, when the pressure equalized, it would suck in dry air to replace the moisture. Again, I wildly unscientific longshot of an experiment.

The hairdryer thing sounds like it would work, so thanks for that. Again, a bit tough to try in the winter, especially since I let me wife have to only available spot in or garage right now. I'll likley replace the housing in spring.