I have a 2002 F150 supercrew. when the interior lights are on, everything is fine. when they turn off after a few seconds, then the headlights go on and drain my battery down fairly quickly. So i have either the headlights or the interior lights on all the time. I have to disconnect the battery cable everytime I leave the car so it wont drain. any ideas?

 

Sounds like a Wet GEM ( Generic Electronics Module ).

Quite a few threads on this topic.