Replacing the head unit solved the problem. Sound from all speakers again.

I think I'm a little closer on this. Per wiring diagrams here - http://www.volvowiringdiagrams.com/ - the three speakers that work (front doors and subwoofer) are driven by the amplifier. The other four speakers are wired directly to the H/U via the grey rear connector. Looking like something wrong ...

Hi Guys, First post here. Looking for some expertise on Volvo audio systems... I recently bought a 2004 V40. It's got 7 speakers - L/R front doors, L/R dash, L/R rear pillars and rear subwoofer. Currently, sound is only coming from the front door speakers and the subwoofer. All four of the other spe...