Mercedes C200 1996
 

Hello I am new here so sorry if i post on the wrong place.
So i have bought a second hand Mercedes C200 year 1996 it is in verry good condition but i have verry strange problem the sensors work wherever they want - when i start the engine one time the speed merer works but the sensor for tempreture dosen't the next time is the opposite. When i whent to check it on the computer the technican says that there is no enought electricity in the board computer and the Checking computer can not read what is wrond do some one have an idea - sorry if i do some mistake in the explination but this is my first Mercedes. The last car i had didn't have so much electronic so i am new in this problems.
Thanks in advance