Hi All, I know this has probably been asked a thousand times, I have just installed a sony stereo in my 02 audi A4 but now the rear speakers dont work. I know this is a common problem but I would like to know whether this is a easy fix? Stereo is a MEX-BT3900U. Im using the loom that came with the stereo although I had to *******ise it slightly to add both the Yellow and Red cable from the audi to the red going into the Sony. Help greatly appreciated.