Help with installation of replacement radio

[spielfreek]

I am trying to replace my CRD-22 with a Sony BT3600 into my 2002 boxter. The Sony unit has Bluetooth phone, AUX and USB which I use every day in another vehicle.

The Sony comes with a lead which terminates in a standard ISO plug which plugs into the car ISO socket. I have purchased an adaptor which allows me to connect the other socket (which has the audio line in connectors) to the Sony line outputs. Looked like a very easy install, except that I hear no music!!

The radio powers up fine, and if I plug the Sony line outputs into my small travel amplifier I hear the music fine. I can also confirm that the music reaches the pins at the end of the wire so there are no faults in the adaptor wiring and the audio is going to the right pins. It switches off and on fine with the ignition, and I've measured the voltages on the ISO connector and they are identical to the voltages I get when the CDR-22 is installed, except the arial/amplifier control pin reads 12V for the CDR-22 but only 10.9V when connected to the Sony. To push the voltage up, I connected a 10ohm resistor between the 12V and the control pin but this had no effect (apart from raising the voltage on the control, of course).

The only missing pins are the "speed" one and the "illumination". It's as if the car amplifier just refuses to switch on. Does anyone know how the amp turns on or spot what I'm doing wrong. I seem to have measured and tested everything I can....