Why does the battery on my 2003 Ford Taurus Drain Overnight?

Answer 1

Could be a bad battery or else there is something drawing power like the radio

if you have an ampmeter put it in series between the battery + and the + connection make sure everything in the car is switched off the reading you get should be less than one amp

If the reading is less than one amp then your battery is probably bad most garages will test the battery for free

If the reading is over one amp then there is enough power being drawn to drain your battery.With the amp meter still connected start removing fuses one at a time and check if the reading drops below one amp putting the fuse back before you check the next one when you find the fuse that causes the amps to drop check the fuse box cover to see what the fuse is for.

example:the radio fuse causes the amps drop below one amp then your problem would be with the radio circuit it could be a faulty radio or just that the radio isn't switched off.

checking this way will rule out where the problem isn't and will hopefully lead you to the problem it could be something as simple as a boot(trunk in America) light staying on all the time

remember that there will always be a very small draw well below one amp as there are parts that always have power like the car clock,radio memory,ecu etc

never disconnect a cars battery if the car has an ecu (most modern cars do)without checking with the main dealer first as it could upset the cars ecu engine control unit