96 windstar stereo doesn't work

On a 96 Windstar the factory stereo/cassette doesn't work.  The display is blank.  I checked the fuse for the radio (#17). I checked for power on the back of the radio, but I think there was only power on one wire.  Shouldn't there be a constant and switched power?

Do I have the wiring schematic right?

Gray plug

lt Grn/blk Constant 12V

Blk plug

Or/grn  LF+

Small plug (rear control)

Where is the source of the switched power if that is the problem?

If I install an aftermarket radio, what do I do with the rear radio control wires?  Does that function just not work with aftermarket radios?

Thanks for the help...

Fixed the radio.  The fuse for the switched power was dirty.  I took it out and scraped it off and then everything started working.

What's this about a common ground system.  Each speaker has a ground and a positive.

I don't think the rear controls will work with an aftermarket radio.  There are only 2 wires for the rear controls, and there is a seek, volume, band... back there.  I wonder how they do all of this with only 2 wires.  It must be some sort of digital signal or it goes through a computer somewhere first.

I guess all is well for now.  If I end up putting an aftermarket stereo in, I guess I will just not hook up the rear stuff.

Thanks for the info.  There are 8 speaker wires going to the speakers.  A positive and negative for each one.  They are all separate at the plug on the radio.  How is this a common ground?

Don't other Ford radios wire up the same as this one?  Maybe one with CD.  Would those have hookups for the rear controls?