left side not playing loud

[1994Vib.RedGT]

so off and on my stereo will have this odd problem where the right side speakers will just blare, but the left is barely audible. I have the stock head unit and some oversize pioneer speakers, I know nothing about stereos, so does anyone have a starting point for figuring this one out?

 

[2BADSTANGS]

Start by checking wiring connections on everything. At the head unit, amps if ya' got em' and speakers. Do a "wiggle test" while the sterio is playing and see if you can get the problem to present itself...

 

[32ValveRom]

I sorta have the same problem except my driver door speaker gets really quiet except for the bass. I'm hoping I don't have to replace anything