Sunfire Rear Speakers Intermittant Sound

[fmjoker]

I have had a problem with intermittant rear speaker sound for a couple of years and thought it was a loose connection in the head unit - I have a 2002 SE Sunfire with the Sun and Sound 6 speaker package. I just had the unit replaced with an aftermarket one and still have the same problem. I know that the speakers are not blown, and am pretty sure that the wire connections to the rear speakers are secure. Last time I heard them come on was about a month ago. Does anyone have a clue what causes this? Do I have to run new wire from the harness to the rear speakers? Thanks in advance for any advice.