This is a weird problem. I haven't dug into fixing it yet, but, my left front door speaker on my '98 Explorer will sometimes quit. Most of the time when the speaker cuts out, I can turn the Heat/Air controls on the dash over the console tray in such a manner or sequence that the speaker will come back on. I haven't found out the connection yet, but it seems goofy. Some day I'll dig in and look at the wiring, etc.
maui