Need Help With 1983 Celica GT

I. Electrical

I have a 1983 Celica GT. Last week the voltage meter on the dash board
was reading about 14 volts (normal is 12). This week, the reading is
below 11 volts and the red light next to the meter as well as the brake
light is on. The alternator tested o.k. and i changed every belt (all
3).

II. Temperature

The temperature gauge almost always reads above the 50% mark. I've
changed the thermostat, flushed the radiator, and changed the belts.
There is no leakage of the water pump. When the car idles the
temperature increases gradually, and when the air conditioner is on it
run HOT when idling. I checked the fan clutch by thumping it after the
car has reached operating temperature and it moves maybe a quarter of a
turn. Changing the belt seems to have lowered the reading to 50% when
the car is in motion, but the temperature outside is cooler now and I'm
not sure if that has a significant effect. Is this normal operating
temperature and if not, what could be the problem.

Any Assistance Appreciated!!!