Car stereo works but has no sound?

I have installed a car stereo. It works fine, but when I turn the ignition on no sound plays from the speakers?

• The stereo continues to work after I have turned the ignition on or started the car and the display tells me that there is a song playing but no sound is outputed from the speakers. Also, when I turn the music up to a certain volume (connected directly to battery) the fans turn on in the aircon. Please help me. This is a very strange problem that I do not understand

• Answer:

  Sounds like you may have a factory amp in your ride. Your best bet if you havent done this is to get a wiring harness for you car. Usually sites will tell you if it will fit and if you have a factory amp in your car. Its either that or something is hooked up pretty wrong. Im almost certain you need a harness though. Check out crutchfield.com. Hope this helps!!