Re: C3 SRC iPhone and Zumo
the zumo 550 does not support A2dp stereo bluetooth protocols, It is mono only when playing music (xm, mp3 from the zumo) I do not think it will work properly the way you are trying to use it. I would try pairing the iphone to the C3 bluetooth so it can stream stereo music, the i phone itself will mute the audio when the phone is used as a phone.
Then pair the zumo 550 to the C3 as a gps only......It might work correctly that way but you will not be able to use the zumo to answer and make phone calls. Kieth
If you pair the iphone as a phone only to the zumo you will get control of the phone on your zumo screen, Use the zumo for your music source and then pair the zumo to your C3 as a headset. It will still not be stereo but it should work..