I have a 2006 Focus Zetec Climate, had it since December 2013, since I got it the passenger side speaker and tweeter in the front haven't made any sound. No idea where to start... I switched out the speaker from another focus and still no sound, wondering if it's a wiring issue/cd player issue. Any suggestions?

Wiring is the most likely, I would think, but the Head Unit output could be dead, too (partic if there was a short across the output). The most likely places for a problem with the wiring are the connectors, where the wire bends as the door is opened or anywhere the wire might get trapped.

Hey BOF, how should I go about checking that?

Look at the wires. If there are any breaks, that would be a problem. If there is a short between the wires, that would be a problem.

You might measure Ohms with a DVM. If you measure across the speaker (at the speaker), you will probably get a value about 4 ohms. You should get a very similar value measured from the Head Unit end. If there is a very low value, then you are looking for a short between the wires. If you see a high value of resistance, then you are looking for a break in the wire. You should also test for shorts to ground.

If the head unit end is difficult to get at, you could also pull the connections off the speaker and test for low resistance to ground, or low resistance between the wires. A bit more difficult to check for open circuits, but I'd expect both wires to sit at 6 volts with the head unit on, but no signal present....but it could be something else (maybe it is AC coupled, but I wouldn't have expected that - it should be doing the same as the working side though).