I am not a professional, but an avid Explorer owner (I am on my third). What you are describing sounds like it might be as simple as a headlight relay. Sometimes, the contacts stick together, causing the circuit to remain energized. In other cases, relays coils may fail, causing a "normally open" circuit to become closed. This is usually the case with cars that have alarm or remote entry systems where lights are flashed upon activation, regardless of the headlight switch position. Just a thought.
It does no harm to disconnect the battery when working on a vehicle but in general no, you do not need to disconnect them to change a filter.
Disconnect the negative cable.
Headlights should not be left on while the vehicle is not in use. If you are not driving, you will just drain your battery while having your headlights on.
If you are talking about disconnecting a battery in a vehicle, yes.
Negative.
Disconnect the car battery, and reconnect it
A vehicle alternator keeps the battery charged It allows you to use the vehicle accesories while driving ( headlights , radio , etcetera )
Without written permission from the NHTSA is is illegal to disconnect the air bag on any vehicle.
Disconnecting Auto Battery Terminal ConnectorsYes, it is safe to disconnect a "car" battery while it's raining, IF you do it properly.When disconnecting a vehicle battery, raining or not, ALWAYS disconnect the NEGATIVE [--] terminal first, and when reconnecting, always connect the NEGATIVE terminal last.
Disconnect the battery. Alternatively you could run a wire from the ligter of the towing vehicle to the battery of the towed vehicle.
Disconnect battery from vehicle - if this still happens battery is probably shorted internally and requires replacement
Disconnect battery for about 10 mins. or have vehicle scanned to determine problem and have code cleared