Yesterday, the speakers weren't working. I set the volume to max for a second and both rear speakers started working, but tomorrow I started the car and the speakers are not woking again

The fader is on 0 and the connections on the radio's back are ok

I'm positive this fault has been discussed before, but on searching the forum, I get 46000 results! (search function is useless!). Hopefully someone sensible will be along shortly If the worst comes to the worst, a replacement head unit only costs about £20 on Ebay, though I note you are not in the UK.

Some good info on here 

 

I have had my 2007 Focus for three years now, and the rear speakers worked when I got the car, but haven't worked for the last year or so. I think I remember reading that the speakers are poor quality, and are known to fail.

I am about to replace the rear speakers on my missus car (mk2 station wagon) now because they are shot. Absolutely not working. Started with getting a used unit because i thought that had failed, but to no avail. Tried with another speaker and that was music to my ears, lol. Hers also got silent, then started working again, and then nothing at all. 

Following this, I keep meaning to see to mine