led wiring

hi all i have 1 LED that needs to be controlled by two different circuits but the problem is that one circuit is const +ve and switched -ve and the other is opposite const -ve switched +ve im having a mental blank and can figure it out.. Thanks Andrew

Use a relay to convert the polarity of one of your sources.  Use the relay on whichever circuit will only be on when the vehicle is running. 

https://www.the12volt.com/relays/page1.asp

Use a 2n3904 NPN transistor on the (+) switched output and convert the (+) to a (-). (any general purpose NPN transistor should work). Connect the base to the (+) output through a 470 ohm resistor. Connect the emitter to ground and the collector is your new (-) output. These parts can be picked up at a local electronics retailed (like Radioshack) for under $2.Kevin Pierson

Or 2 else 4 diodes if my intuition is right (ie, a bridge rectifier).

will try the transistor method as i happen to have one here. Thanks