LED Remote, Isolating 2 channels
Your diodes appear to be connected backwards. Current flows from Anode to Cathode in the direction of the arrow, which needs to be towards Ground. I have modified your diagram with the correct diode polarities, and showing the complete circuit with what (I think) is inside the black boxes. 

Two diodes between the LED strips and the ignition relay contact would probably be enough to isolate the LED strips, but the extra ones won't hurt.