C280 Coolant Temp High at Idle

[vince]

1995 C280. New water pump, viscous fan clutch about 20K ago. At idle coolant temp climbs slowly to mark above 80C on guage. With the climate control on it climbs somewhat higher, over the mark above 80C. Temp is fine when car is moving. NOTE: It is doing this even at ambient temps of 60F. To me it seems like an airflow problem. Question: Does the auxiliary fan come on at elevated coolant temps, or is the viscous fan clutch totally responsible for additional air flow in this case? The aux fan does come on intermittently, but it seems to be in response to air conditioning compressor high side pressure. If there is a switch to control the aux fan, where is it and at what temp should it activate? Is there a relay? I wish M/B would publish a manual!!!