flashing led deterrent.how to wire?

i don't want to sound painful with this but i just can;t figure it out no matter how much i search the net.. you place your flashing led (acting as a deterrent) in somewhere nice and obvious, wire up the +ve to a constant positive, wire up the negative to accessory. when the car is on it sees +ve on each side so sits there doing nothing... on ignition off the +ve which was going to the negative lead is opened so it earths through the accessories wire so i can see that it would then start to flash. Problem solved... but aren't the accessories on the wire, like your stereo for example going to try and draw current from the constant +ve through the LED? I understand that the LED is going to act as a resistor and will draw maybe 20mA or so itself but the complete circuit of constant +ve through LED, through accessories to earth would seem to me like the accessories will still try to draw current... heeelllpppppppp... it's driving me nuts, i gotta' be missing something. if you have your stereo switched on when you get out of the car, it'll have the -ve, constant positive and then it will try and draw a accessory switched +ve each time the LED flashes wont it? cheers

Bobk, I was about to post a similar reply to your last one, until I saw it. You are absolutely correct about the diode.moshpitmickey