c class 180 model 1996- electrical problem causing highest temperature and problem in starting the car

i changed the electrical installation that
comes above the engine. after that in a
while, i have difficulties starting the engine, 8
to 9 trials.. afterwards it works fine. however
from time to time the temperature shows 120
at red and the fan starts for like 30 seconds
and then it comes back to normal. what do
you think the problem might be?!