I installed a Pioneer flip-out screen and it works fine but there is no sound because I don't know what factory wire I connect to the blue wire that powers the factory amp. I tried connecting it to the power wires but no luck. Please help!
You need a radio that has an amp-out wire...check the harness or plug wire diagram.. or RCA jacks for an amp which can be converted to speaker wire which you can attach the the blue amp wire....the following link has more info. Check the harness plug for a terminal/wire in the letter "I " position...that is for the amp.
Alternatively, some installers hook up the blue wire to switched power and install a 1.5K resistor in the wiring for the correct power to the amp.
http://www.ford-trucks.com/forums/860918-aftermarket-head-unit-with-factory-amp-sub.html