I have only my passenger front speaker working. Both rear tower speakers and the driver front speaker connections show less than 0.1V @ maximum volume.

Note: my radio gets very bad reception, I don't know why. Antenna or dirty/loose connections behind the stereo maybe?

I have tested these new Kicker DS40 coaxial speakers (4ohm, 4 inch, 50 watt peak, 25 watts rms), and no sound. I tested them on a 9V battery and they work.



I tried the stock speakers, (10 watt, max 25watt) and they don't get sound either. Passed the 9v battery test.

So are my speakers not working because of the low voltage at the connections? How do I fix it?

 

depends..
are you going to state on which series of car this is on?

The FC has stock amps..so if you bypass the amps and run direct from the stock unit to the speaker you get ..well hardly anything.
If you run an aftermarket deck,then wire the speakers direct from the Deck to the speaker(or aftermarket amp to the speaker.
You can also wire from the aftermarket deck to stock wires AFTER the stock amp (bypass stock amp)..those wires go to the appropriate speaker.That way you don't need to run any extra wires.
(but I usually wire NEW ..and leave the old crap on the car.)