flashing lights

So i have a 2004 Ford Explorer 2WD, and my headlight/brake lights will occasionally flash while the car is off. It happens at random. i will go outside and see the lights flashing at the same rate a turn signal would flash. i usually unlock and lock the car again which makes the flashing stop...

So i did have my od light blinking and abs light on so i replaced the vss and the abs hasnt turned on since, only problem is that the od off light blinks continously once the truck warms up. it has no shifting problems what so ever, actually it shifts like a dream! any advice? i just bought it...

This morning went out to start my 99 explorer. Turned the key and got the clicking sound of a dead battery. Put on a charger with a start feature and did the same thing. But what was most interesting is that the lights etc on the dash were flashing and the speedo or tach was jumping up...

my 99 explorer xls 4x4 has started flashing 4wd hi and 4wd low when i start and periodically when i drive. i almost never use 4wd. does this indicated a transfer case problem or something else? if transfer case, what happens if i ignore it. money is very tight. thanks