Audio Systems: radio power no sound, ford conversion vans, factory radio

Question
The sound on our 97 Ford Conversion Vans radio quite working about two months ago. The display works fine and you can change the channels fine but no sound. After many trials at diagnosing the problem we realized that with the van off and the key turned to auxilary and the battery loaded down (power windows max, power seat max out, headlights on etc...) the radio will play until you start the vehicle and then it's back to no sound.
We've chnaged back to the factory radio, ran a new ground wire, and even ran a wire direct from the battery all to no avail.
The local garages are clueless.
Any ideas?  

Answer
Mike,

 i can see why they are clueless, it sounds like something in the main wiring harness but since you've ran new direct wires that should have taken care of the problem... i dont know what to tell you aside from trying maybe leaving it with a shop to see if they can trace down the problem


thanks

CM