Audio Systems: factory amp, car radio wiring, rca input

Question
on a 2002 expedition with mach audio system sub not working i replaced radio with after market along with all in door speakers now i want amp and sub to work. i hooked speaker up to amp and got nothing so are there fuses or what should i do next?

Answer
Better check the wiring as this is a common problem when going with aftermarket head unit.

Here is a wiring guide:

http://www.modifiedlife.com/2002-ford-expedition-car-radio-wiring-guide/

And, you must make sure the sub output from the head unit is connected to the input of the sub amplifier.  It could be rca/cable to rca input or it could be going through a multi-pin connector since I haven't seen one for some time.

And, you must get the right power remote turning on voltage to the sub amp. Here is a discussion that will help you figure it out, I think:

http://www.ford-trucks.com/forums/653079-01-expedition-mach-audio-sub-amp-wiring

Good Luck.

PS: Of course the subwoofer speaker itself may be open but that would be rather rare. If you need instructions on how to check it you can google for speaker testing.  Look for the thump test using a battery connected to the terminals of the subwoofer and that will tell you if the voice coil is good or not.