Stereo speaker works for radio, not tape player?

[CantonProf77]

I have a '97 Crown Vic that's got some stereo issues. The left speaker works perfectly fine always for the radio, however, it sometimes does not work at all or produces low-volume hiss/pop sounds when the tape player is engaged. I've tried to notice patterns for when it will work or not, and the closest I can come up with is that it tends to work a little more consistently if the cabin is warm. This is the original stereo and speakers I believe, and I have not looked inside anything. Any help is appreciated! Thank you!