Hey, first post here. Looked on search for an answer but couldn't find what I was looking for.
I have a 92 300D with a temperature gauge issue. When I got the car last year the temperature gauge was reading a steady 65°C once warmed up. I at first assumed the gauge was right so I replaced coolant and replaced the thermostat. That didn't work so I replaced a couple coolant sensors including the sender on near the lower radiator hose. That didn't work so I started reading temperature with an infrared heat gun. A few months ago I was reading 80°C at where the upper radiator hose attaches and about the same at the base of the lower temp sender. So I am pretty confident the temp is correct. Checking the temp in winter has been less successful though any I'm getting lower readings at both locations.

BUT I'd like to use the heater fan "auto" setting as a double check that its actually getting as hot as I think it is. Does anyone know at what coolant temperature the heater fan is supposed to kick in?