fading ground and buzzing relay

A  manufactures wiring diagram would help here.John DeRosa (Hotwaterwizard)

Stockton California

When in doubt, try it out !

Not sure what exact part you need but every wiring diagram for the truck is in here... '03 Ram Manual

And thank you for your time

Sweet. You are a GeniusJohn DeRosa (Hotwaterwizard)

Stockton California

When in doubt, try it out !

Care to go a bit more into depth? Do you mean just use the cargo light switch to turn on the cathodes?

Close use the cargo light switch to turn on the relay.John DeRosa (Hotwaterwizard)

Stockton California

When in doubt, try it out !

That still doesn't help me when the doors open

I run into a similar situation when doing a flip-down TV install in a 2004 Ford Escape. The dome light wiring in the Escape has constant 12V to the light, and the ground wire triggers the dome light to turn on when the doors are opened. This was the initital problem I had, which I figured I would use a relay to convert the (-) trigger into a +12V which the TV dome light circuit needed to activate. This was fine and worked when the doors were open and the dome light was on. But when you closed the doors the dome light would fade off, and would make the relay buzz (when turning on and off quickly) as I assume this was done with a PWM signal from the dome light circuit. Personally I was unable to come up with a solution for this in the alloted time I had to do the install, so I just wired the light into a 12V source, and the switch on the TV allowed the light to be turned on and off manually, but was not able to wire it in to trigger with the dome light circuit. If you come up with a solution, I would like to know for future installs of mine as well. Sorry for the long post; just wanted to share my experience as well.

Here is what I think I'm going to do. I'm going hook the cathodes into my cargo light, like hotwaterwizard suggested. Then I'm going to find the wire from my alarm that turns on my parking lights when I disarm/remote start my truck and have it also turn on my cargo light. This way I can turn the lights on with the OEM cargo light switch and they will also come on when I disarm/remote start my truck. Any opinions on that?