'91 Mercedes 190E

anyone ever done a deck on one of these? it has the fader control by the shifter and there are 4 wires comming out of the dash, the customer brought it in, 2 sets of wires were already cut, then there was 2 more sets with the round female plugs on them of the same colors of the ones that were cut, when the speaker output from the deck is hooked up the ones that give output they only  output to the rear, we cannot get the speakers in the door or he dash to work. Anyone have any ideas? the customer states she had a sony radio in there before it was stolen and that all the speakers worked.

the wire colors are,

bown, brown w/ red, grey, grey with blue