My radio is really freaking out lately. As I turn the volume down the speaker on the passenger side crackles and almost goes completely out. However if I turn it up it's just fine. If I hit the dash near the speaker the sound comes back. It sounds like a loose wire or something. I don't know just a wild guess I'm totally car illiterate!!
Just normal scratchy old radio volume control. Get yourself some spray electrical contact cleaner and, with the ignition off, spray a healthy dose around the volume control knob (take it off if you can). Open the tape door and also spray to the left in the direction of the volume knob internals. Work the volume knob for a few minutes to get the fluid in. Do the same for the balance thumb wheel located near the radio. Also work it real good for a few minutes. Wipe up and excessive fluid and wait a few minutes for the excess to evaporate. Should be ok for a while now and just repeat the procedure as required or until you give up, like the rest of us, and buy a Blaupunkt. :-)