The temperature gauge on my newly acquired 820 coupe was reading high by about 10 - 15 deg C when cross-checked with a thermometer.
I surmised that the sensor's negative temperature characteristic curve (i.e. temp rising > probe resistance lowers) might have been tracking too low a resistance and hence making gauge read 'high'.
I fitted a 33 ohm 1/2 watt resistor in series with the lead to the probe and the gauge now reads correctly over its full range and also correlates with the temperature at which the radiator cooling fan turns on and off.
Brian
