This is normal,the anti-theft light will blink to act as a theft deterent.It uses les then 30 milliamps so ot would take several days to weeks to discharge a good battery.
Do you mean that it always continues blinking until the vehicle is started again? This is a spare vehicle that a friend has, and I am borrowing it for a few days while my car is in the shop. They have several vehicles and don't drive this one often, so it does sometimes sit for a long time without being driven. Does that light blink all the time? Tonight is the first time I noticed it when I shut off the vehicle.
Yes it blinks like that when ever the key is turned off.It is part of the PATS (passive anti-theft system).It should blink once every 2 secs.
There is also a chip inside the key so when you turn the key on then if the PATS system sees the chip it will turn on solid for 2 to 3 seconds then turn off.If it does not see the chip in the key then it will start flashing rapidly and will not let the car start.
Ok I am trusting your answer, I hope the van starts in the morning.