OK Arthur - got you on the a/c circuit - my trip this week to warmer climes will tell if all is well. On the engine temp sensor - you have me confused - if it is a negative thermister - lowering in value as the temp goes up - why was the fan test from Mercedes dealership to pull the connector off the sensor and the fan goes on? With open circuit -resistance will be infinity not low. Are we talking about two different sensors???
Please advise
Morris