Bat. Light, Dead Tach, Fuel gauge, turn sig
 

I have a 1983 Volvo DL with 180k. I started it the other day and noticed that the tachometer remained at zero, but then came back after a few minutes. I thought nothing of it. Today as I was driving the vehicle my battery light came on and I lost the tachometer and fuel indicator. The battery light illuminated intermittently as I drove to the nearest parking lot. The tachometer came back just as I was about to make the turn but when I switched the blinker on (left) the tach died again and the blinker did not function. The battery was reading 12 volts with the engine off, charged up to 13.6 with the engine running, so it seems that a lack of voltage is not the problem.
The battery light was still illuminated after running the engine and checking the battery voltage. Eventually the tach came back but when I tried the blinkers again they did not function and it also killed the tachometer. The car does not crank slowly. I haven't a clue what is going on here, anybody have any ideas?

Recap:

Battery light comes on and remains on.
Tachometer is intermittently functional and reads zero when attempting to use the turn signal.
Turn signals are non-functional.
Fuel gauge is non-functional.

"Battery light comes on and remains on."

That indicates the alt is not putting out. Or it's putting out intermittently. Maybe loose drive belts. Or you've got a bad connection, ground, little red wire, something. If the alt was putting out, the BATT light would have the same voltage on both sides and it would not be lit.