I'll rip the unit out tonight to get the part number.

What's the part numbers of the older Nokia ones? And do they just do calls or stream music too?

Wrt the professional installation, the BT was plug and play so it's either not compatible or faulty wiring kit. Ironically the RVC was soldered into the power and can high/low wires.

Liquidforce, what is your perspective on next steps for diagnosis?