Aftermarket CD changer installation

I tried installing an FM modulated CD changer because I'd like to keep the stock radio and have run into a problem with the antenna. The radio is a Becker Grand Prix 2000 w/ automatic antenna (no switch). After installation, the radio works and powers on, the CD changer powers on and scans for discs in changer then appears to start playing, but the antenna does not raise. If I were to disconnect power to the FM modulator (red & yellow wires), the antenna will raise so I believe all wiring is correct since power to the antenna still has to go through the FM modulator. What can be causing this to happen? Please provide as much input as you possibly can. I need the antenna to raise with the changer plugged in.

Thanks,