Originally Posted by captainlaziness (Post 3396529)

Set up a video camera on the inside of the car and have it record all night. In the morning, go turn off your head lights and retrieve the camera and watch through the video, paying close attention around 3:00am. Repeat this process nightly so you can catch the activity on tape to show to the techs at the dealership. If the camera alone doesn't seem to be working, try spreading some talcum powder all over the inside of your car.

Once you have caught the problem on tape, you are going to lose the use of your glovebox and possibly the center console as well. Don't go into the glovebox. I repeat, DO NOT GO INTO THE GLOVEBOX. You really won't like what you find in there. Ok? It will probably be something that seems innocuous at first, like an old paid off ticket, but will quickly become extremely horrifying and problematic.

After that, windows may start rolling up and down or breaking. Radio presets will change and you car may even drive itself over to another car and idle for hours. It's headlights blankly gazing at the peacefully slumbering Mustang at the other end of the parking lot. These bizarre occurances will increase in regularity and violence until the car eventually kills you and sniff your corpse.

Originally Posted by nodsetse (Post 3396493)

It's not surprising that 2 dealerships would cite different causes, as this is truly a strange issue. I don't think there's anything in the service manual's trobleshooting section for the condition "headlights off, engine off, then headlights magically come on by themselves some hours later". Fixes for things like this are often difficult, as you usually can't track down what might be an intermittent short (which can take forever at $$$/hr.), so most places just remove & replace the most likely parts one at a time until the solution is found.

Originally Posted by captainlaziness (Post 3396529)

Set up a video camera on the inside of the car and have it record all night.

Originally Posted by engifineer (Post 3396584)

Except that a good, experienced mechanic knows how to troublehsoot past a service manual ;) A lot of dealer techs unfortunately know how to read a service manual and replace parts, not how to properly troubleshoot. Not all are like that of course.. but lots are. And their labor rates are so butt raping high that it tends to pay off to replace the parts first :P

As I answered on your thread on ystc, go to a private mechanic with a lot of experience. Usually lower labor rates as well.

If it were mine... I would do the following, especially if it happens on its own fairly regularly.

1) Disconnect power to the multi-function (Aka headlight) switch.
2) See if problem occurs again overnight.

If it does, the relay, or at least something down the line from the switch, is at fault.

Doesnt necessarily mean it is the relay either if there is an intermittent short.. but it keeps you from buying a headlight switch you dont need. Next step would be to inspect the wiring to the coil on the relay to look for any sort of chance of a short (although that would probably happen over bumps and such as well) before blaming the relay.

I have seen things happen like this in the cold before.. tended to be the relay before the switch.

Originally Posted by Just_Thu (Post 3397219)

Thank you, got it fixed.

Originally Posted by sciontc_mich (Post 3398627)

so what was it? the relay and if so, which one?

Originally Posted by Just_Thu (Post 3396374)

I have a 2007 Scion. i noticed now that its starting to get cold overnight, i wake up and my headlights are on. the headlight switch is clearly off so its not a user error. i took it to a couple dealerships and one place says its the headlight on/off switch. another says its the relay.... well, which one is it? electrical parts are not returnable so i dont want to waste money on buying both parts. please help!