LED troubles on my DOD 250 reissue (2013)

[Gregmon79]

hey there. Was wondering if anyone could help me. I installed an led in my DOD 250 reissue (2013). But it only lights when just the input is plugged in. As soon as I plug the output in, it goes out. Can you help please??

I have the ground (black) wire going to the same lug as the red wire off the battery to the power supply in. I'd post a pic but I can't seem to figure that out. Hopefully this is enough info. If not, please let me know what's nissing to solve the problem and I'll do my best to provide it. Thanks!!!