Headlights come on intermittently and drain battery.

Hi, I have a 2004 Double Cab Tundra and the headlights will come on for no reason and drain the battery while the keys are not in the ignition and the headlights are in the off position. Any ideas?

 

I’m definitely no electrical expert but I would think that it is switch related.

 

Switch or relay, especially if it's the only circuit impacted and OP did no upgrades.

Could be switch. Maybe someone went with cheap aftermarket replacement on scAmazon, this would be par for the course on scAmazon parts. Have you changed anything on the headlights, upgraded to LEDs maybe?

Any other circuits with issues? Per the megathread of things you need to know, bolded part for your reference:

• These trucks usually don't have a ton of other electrical issues. Hidden corrosion inside the battery/alt cables happens. Sometimes, a couple thousand miles after timing belt changes, people will have startup issues because the crank position sensor wasn't properly tucked away and gets rubbed by a belt (pic). There's also a similar problem with camshaft position sensor under the cam cover, where the belt will rub through (pics). There's the rodent issues mentioned earlier. Occasionally, water leaks can send water down into the ECM behind the glovebox (pics), or into the fusebox inside the cab/dash (pics & pics & pics, it happens a LOT). Many drain/vampire issues trace back to aftermarket add-ons whether the owner knows they exist or not - alarms as mentioned earlier, brake controllers, poorly installed trailer receptacles, those are some big ones.

 

Seems like every time this happens it ends up being water in the inside fuse block.

 

Could be a sticky relay as well.