Yes i've check the balance and fader settings. i wish it was this.
Bearing in mind my system should be providing a speaker level output. i'm getting about 200mV from the front right, 100mV from front left and virtually nothing from the right rear and nothing at all from the rear left.
Out of curiosity i connected it correctly to the amp and there is enough signal from the front channels to get sound if i turn the gain up on the amp and offset the balance to compensate for the difference between the left and right channels.
I'm guessing that i have blown the puny power amp in the head unit.