Audio Systems: install head unit, car audio shop, radio shack

Question

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Followup To

Question -
I installed a head unit and it turned on but the speakers dont work

Answer -
I need a bit more to go on here,
Head unit? Make & model would be good,
Does the new head unit function as it should apart from being mute? Have you check for a "Mute Button"?
Speaker set up, what do have and it as is was before or have you made changes there?
Are there any amplifiers involved?
Did it work on the old head unit and have you swapped it back to see if it still works on the old head unit?
 

it is in a 93 lincoln contanintal and the head unit works but there isnt no sound i heard the car has a factory amp but i dont know so i put back in the factory and it works fine

Answer
No expert on Lincoln but it sounds like you are not puting 12v to the amp, this is the blue wire out of the head unit without which every thing will work but without the amp it will be silent. I would reccomend a DIN to Lincoln loom adaptor from radio shack or your local car audio shop.