amp not getting input?

I have a KENWOOD KAC-9152D that has both speaker level and rca inputs I tapped my back speakers and tried using the speaker level inputs. It didn't work. I hooked up a portable cd player to some RCA's and plugged them in and the sub fired and worked so I thought the speaker level inputs were not working. I went and got a line out converter, still using the taps to the rear speakers, I hooked up some RCAs and it worked for while. Then the sound cut out. I thought the LOC was bad, but hooking up the RCA output to some headphones, I got sound. So I know the LOC is working and sound is coming out. So it seems like the amp isn't taking in any of my sound. I'm not sure where to go from here.

Check the speaker wire on the amp to the sub and make sure it is not grounded. The subwoofer is shorted and damage. The RCA connector may have fail and only works half of the time. These are common area I would look into and that I can think of at the moment to help you out to pin point the problem. Be careful whose advice you buy, but be patient with those who supply it.

thanks, I've tried more than one RCA wire, but I'll be sure to try yet another one I'll also look into the speaker wire issues and see if that is happening.