I would check the easiest first, coolant temp. sensor. The resistance should be around 4K ohm (I am not sure what 44F is in Celsius). The resistance should drop when the temperature increases. At 40C coolant temp. it should be 1K Ohm, at 80C 300 Ohm. These values are from the MB 103 engine manual but they should be the same. If the resistance is infinite replace the sensor.