1984 240DL Won't start

I 've had this car for 6mos. no real problems.
-a few days ago I noticed one tail light out.
replaced bulb nope- ran wire from one to the next and
got it to work.
Next, today the radio cut in and out and then just died?
but the cigar lighter still worked? (same fuse).
Then several hrs and 40 miles later I turned off the car and now it won't
start. just cranks.
the dash lights and gauges don't change when the key is turned on interior
light comes on and radio lights up but no digital display.
Please
Help

 

The tail light is probably either the bulb failure sensor (easy to resolder
the circuit board inside) or the plug where the wiring harness plugs into
the light assembly. Your other problems sound like oxidation in the fuse
panel, there's multiple terminal lugs that wires connect to coming off of
each fuse, if water gets in there it corrodes.

 

Could it be just a dying battery? I only ask because when mine had a
starting problem the battery got low but still cranked as if it was OK, the
starter would not disengage and it kept cranking after the key was turned to
off. Other weird things might also happen with low voltage.

 

It was oxidation and a bad fuse, all is well.
I haven't checked the tail light yet.
Thanks so much