With more than 900 pages of R170 SLK forum, I could not find an answer to my problem. Please help. I have a 1998 SLK 230 with 30K miles. Recently the car has been overheating. I have replaced thermostat, coolant, spark plugs and cooling fan control module, but still no improvement. When outside temperature is about 75 degrees and the reading of the temperature gauge reads 105 -106, the cooling fan does not turn on. When I jump the fan directly to the battery the fan runs at high speed. I have opened the k40 relay looking for defective soldering but all looks fine. I have read in this forum that there are other owners with same problem but could not find a solution or guidance to help solve the problem. Could somebody please help me. Thank you in advance.