Ok, so I read the whole thread, and I am stuck here in the EXACT position, a half hour away from picking up my son at school (my mom's on her way) and I am FURIOUS!
Basically, same issue... mine's a 1983 300TD Wagon... have had issues over the past month every few days... I get in, and turns over once or twice slowly, then nothing. NOW, after fiddling with the antenna all day, got it working (well, receiving reception... unplugged it), went to start it up and nothing but this f***ing buzzing from the GP relay box. First time for the buzz. I've jumpstarted it in the past and it ran fine the rest of the time, until randomly, would not start. Tested voltage with everything off at battery... 12.6 or something like that. Turned key on, drops to 7.5ish. Not sure if that's normal. My radios actin' all crazy... dim lights and ****... like there's a cross somewhere, but I'm almost positive there is NOT...
Low voltage would be caused by faulty voltage regulator? Or does that only function when running? Or faulty alternator? or battery? I bought a new one 14 months ago. Just don't get it and am frustrated....
No loose cables or belts... just up and started getting testy on me.
Leavin' it to the pros on this forum... y'all are way too smart to let this one stump you.