No sound from rear speakers On Jetta

I have a 1995 Jetta with the premium sound. I don't know if it uses an external amp, but here is my problem. I bought a wiring harness and a sony head unit and wired everything correctly (or so I'm 99% sure). The sound from the front speakers is perfect but there is no sound from either of the rear speakers. I did wire the antenna and amp blue and blue/white leads, but when I looked at the factory harness connector, there is no leads going to those places on the plug. What could be the problem? The rear speakers worked before with the factory head unit. thanks, Matt

Whell, you have a sony head unit.... ahem... anyways, try switching the front wires to the back and vice versa.  If you do that you can either narrow it to the car or the cd player.2003 Chevy Avalanche,Eclipse CD7000,Morel Elate 5,Adire Extremis,Alpine PDX-4.150, 15" TC-3000, 2 Alpine PDX-1.1000, 470Amp HO Alt.