Resistance is your problem. The LED bulbs use so little power that when you put them on a 12-volt line they are fried by the excess voltage.
In order to stop this, you'll have to put a 'heavier' resistor in the lin es.
There is a mathematical formula for computing the resistance (OHMs)
that yhou will need for each line, but,,,,, I can't remember what it is.
You can also 'google' emergency vehicles and find out where they get their 2 and 3 flash signals.
Someone at Radio Shack should be able to help you.
