power and ground for satellite radio

All I'm trying to do is to splice in a power and ground (that is attached to a 12v/5v convertor for my satellite radio) to the power supply on my 12v accessory output.  I hooked up the (+) wire to the red wire behind the bezel, and hooked the (-) wire to the black.  I got nothing.  Do I need to actually physically ground the (-) wire to the vehicle?  I assumed that simply splicing in the (-) to the black ground already hooked to the output would do the trick.

Anyone with any ideas?

Ouch,  no one else had this problem?

I'm not sure if the ground just isn't making good contact or what.  You could clearly see wire exposed where the wiretaps had been clamped once i took them back off...

Just thought I'd check back one more time in case anyone had any feedback

To further clarify, for those not blessed with the power of deduction from my SN (no worries, not your job, i should have indicated previously), we are talking about an 01 GC.  The bezel I'm referring to is the lower bezel on the middle console that houses a fold out ashtray as well as mounts for two 12v power output sockets.  Having already mounted the xm radio unit in the foldout compartment that used to be the ashtray, and running the antennae to that location as well, my only obstacle is tapping the power source with my 12v-->5v adaptor which is what I was having problems with.  I've used wiretaps/quick splices before, and never had this problem, so I'm just curious as to whether anyone had this issue before.

I know it's the power and the ground because that is the only two wires going into the back of the accessory output...also that is how the wiring diagram

http://www.wjjeeps.com/cargo_12v_wiring.jpg

Let me also add that im not using the supplied adaptor that looks like the standard accessory plug...this is an adaptor specifically made for the expressed purpose of hardwiring a power supply to this XM radio from a 12v source and knocking it down to 5v for the radio...