A 94 c280 has alot of faults, I have experienced problems with the OVP relay. I usually dont replace thermostates until they cause a problem . Main problems I find on these cars is the trans, engine , and harness for the EA. The head gasket timing covers leak oil . Otherwise really good cars. I have had people bring me cars like this that they just bought and say fix all the common problems and then they dont have many problems after that. Do your maintnance on time and take care of your car and you will be ok.