HU Toast?

I have an old Sony CDX-C780 I want to throw in this '84 Caprice I have.  All the wiring seems fine (colors, etc) and for a constant wire I just stole the power wire from the blunt lighter.  Problem is, if the antenae is plugged in, I can't control the deck - all controls cease to function.  If I unplug the antenae, no audio comes through.  And come to think of it, I can't seem to get audio to come through the speakers at all most of the time.  Once or twice I actually had a CD playing fine, with audio coming out of the speakers fine, except I couldn't control anything at all.  I figure something has gone inside the HU but I don't know what it could be - at one point or another I have managed to use the HU controls fine, and I have heard audio through the speakers (also good).  Just can't get any consistency or full-functionability happening.  Any thoughts?

Jay Cadilak, peace&unity

UPDATE: Ok, the control issue has been solved.  However, I still can't maintain constant audio output.  If I fiddle with the flipdown face, the audio will kick in but eventually (and much sooner for CDs) the audio will completely cut out again.  The unit is still functioning properly when the audio goes, but alas no audio.  My guess is inadequate power cables.  They're all the stock Caprice wires and the constant power from the lighter didn't quite reach so I had to add an extender piece to reach the wires on the back of the deck.  Maybe the HU has a feature that shuts off the amplifier if the unit doesn't receive enough power?  So my next option is re-wiring totally.  A hassle, but definitely worth it.  And hopefully its not a weird short inside the HU...

Jay Cadilak, peace&unity