I have a 1992 C2500 with just less than 35,000 miles (really!) with the
AM/FM radio with the cassette deck. The radio's clock always reads 10:49
when off, and when turned on, it shows that it's tuned to 1230 AM with the
volume halfway up. However, there is no sound coming from the radio, and all
the buttons except for the power are virtually unresponsive. It does sit
parked outside most of the time in the varied North Carolina weather. Could
this have something to do with it, or is the problem somewhere else? Has
anyone even heard of something like this?

Is this one of those radios that has a separate cassette deck located
in the middle of the dash?? If it is then I suspect its the micro
processor box that sits up under the dash. This type of radio is
actual a multi piece unit. you have the head unit, the cassette
deck, the box and then the optional eq. I currently have the same
problem with my 92 1500. After a few tests my electronical buddy has
determined that the brain box is dead.

Snow...