i bought a used 01 expedition w/an aftermarket (pioneer) head unit installed.

i noticed that the rear (door) speakers weren't working and i assumed that the previous owner had a set of speakers that he had removed when he sold the vehicle.

to remedy this, i purchased a new set of speakers for the rear doors. when i removed the door panel, i found that the facory speakers were still intact and plugged in.

my next step was to remove the pioneer head unit and see what kind of wiring nightmare i had to work with.

as i suspected, the factory wiring harness had been spliced into to preform all the connections.

i went to a local mobile audio store and purchased the factory harness adapter to make the installation much cleaner.

now i've wired in the head unit correctly and still there is no sound from the rear speakers. the front speakers work fine, as they did before i re-installed/wired the entire system.

i plugged the adapter into the factory wiring harness and checked the continuity from the adapter wires to the individual speaker wires on each door. the speaker (-) wires from each door were continuous from the dash to the door. however, both the speaker (+) wires were not. there is an open circuit between the dash and the rear door speakers' (+) side.

my factory speaker grilles say "PREMIUM" on them. however, i have no idea how this vehicle was equiped before the original owner removed the factory unit.

i suspect that this is a factory amplifier issue, but i'm not sure.

can anyone tell me a possible solution to this problem?