A note here from an electrical engineer. The LED itself only draws maybe 20 milliamps. 20mA x 12 volts is .24 watt. In the above circuit, there is a secondary current path to dissipate through that parallel resistor. You would need a 48 ohm resistor to draw 3 watts. Now, here's the important part. 3 watts as a fair amount of heat so you want to get a resistor that can be mounted to a heat sink. I would think that the firewall should be fine.