How can I make my rear speakers in my 01 VW Jetta produce sound?

I just bought an 01 VW Jetta and everything in the sound system sounds great except the rear deck lid speakers produce no sound. The rear tweeters in the doors work, as does every other speaker, but the rear ones don't work. How can I fix this without throwing a great deal of money at it?How can I make my rear speakers in my 01 VW Jetta produce sound?try adjusting the balance