dual triggers for relay diodes required?

Sorry for if this is a newbie question, but after a few searches, I haven't been able to find a similar thread. I have a 2000 Ford Excursion. I plan to install a set of auxiliary back-up lights. The lights will be powered by the back-up light circuit off of the towing harness. Simple enough, but what I also want to do is install a switch at the dash that will allow me to turn the lights on without having to put the car into reverse. I have found the relay in the engine compartment that controls the back-up light circuit in the tow harness. I plan to connect a powered switch to the relay as a second trigger source. My question is: should I install a diode on both the new trigger that I am putting in as well as one on the original factory trigger? Thanks in advance. Brian

If you don't install a diode then most likely the OEM back up lights will come on when you flip the switch.  If that's not a big deal then you should be able to leave the diode out.  If you only want the added lights to come on then a diode would acomplish that.Kevin Pierson