Bose problem

I have a 98 Nissan Maxima SE with the Bose sound system in it.
Recently, I've been having problems. At first, it would be playing
sound through all speakers and after I'd go over a bump, it would for
some reason just play through one speaker. I would then just move the
volume knob a little bit and it would start playing through all of the
speakers again.

Now, however, it ONLY plays through one speaker (the lower speaker on
the driver's door). If I put my ear right up to the lower speaker on
the passenger door, I can hear a little bass but not much. I have
recently noticed that when I turn on my headlights, the display does
not dim and the lights behind the buttons do not come on. Also, the
balance and fade knobs have no control anymore of where the sound
comes out of - only that one speaker. I took out the system and made
sure all of the wires were in securely and nothing was frayed, and it
all looked ok. Any ideas?

If possible, get another head unit and plug it in to your car, if that head unit can make your speakers work without any problems, fader, balance, etc. then I'd say the problem is definitely not the speakers and more likely than anything you need a new head unit.

If the test head unit however, has the same problems, then, more likely than anything, it's the speakers and/or the wiring.

Good Luck.