Anyone help determine if the cooling fan clutch is not engaging properly? When the 1995 SL500 is cold, and it is cold in Cleveland Ohio today, 20 degrees, the fan can be rotated with very little effort. I drove the car for its mid-winter excursion for about half an hour at speeds of 50/60 mph. Thermostat showed the temp in the 55/60 celsius range. Got heat from the heater but the dash gauge was in the very low range for this car. On warmer days, the temp is typically 80/90 celsius and I have never checked to see if the fan clutch activates. I thought that since today was especially cold outside and that the engine never really warmed up into its usual heat range, that I might not be able to determine if the viscous clutch is working or not.

Here is the question: At what point or temp should I expect the clutch and fan blade to "lock-up" and become harder to turn with the engine off? Its not doing it now but again that may be for the reasons mentioned above. Thanks, Steve