Factory AM/FM/cassette digital radio in my '82 Lebaron was sounding real bad so found a radio from an '83 Dodge AM/FM radio w/manual tuning in a salvage yard. Worked great (other than the tuning seemed to "wander") for a the last year and a half since I installed it. Right before I put it away for the winter the FM part quit working. I drove it in the late fall and I know it worked, my son drove it about a week later and said the radio didn't work. AM side still works. My son said he didn't touch anything other than the tuning knob to try to get some music. Thoughts on why the FM side suddenly quit working and how to fix?