Hi All,
So I was poking through the Fuel System section of the E30 Bentley manual and noticed that the tables for testing the resistance of the coolant temperature sensor only contained 3 values (14 °F, 68 °F, and 176 °F). This skips a large range of ambient temperatures that the coolant could be at when testing the sensors, so I decided to use the values Bentley provided and generate a more comprehensive set of values. I plugged in the Bentley values into the mycurvefit website and generated equations using a Half-Life Exponential fitting method. In the equations below, the x variable refers to the coolant temperature in °F. Note that the equations are derived from the 14 °F, 68 °F, and 176 °F values provided in the Bentley, which states that a ± 2 °F margin of error for coolant temperature x is okay. Note that the E30 Bentley manual does not provide values for the M42 engine. The E36 Bentley manual shows the coolant temp sensor resistance values for the M42 that are the same as the ones for the M20B25 in the E30 Bentley manual. Based on that, I am going to go with the assumption that both use the same coolant temperature sensor.
M20B25 and M42B18 (blue connector):
Coolant Temp Sensor Minimum Resistance: 170.3153 + 11469.55 / 2(x / 27.21654)
Coolant Temp Sensor Maximum Resistance: 214.9207 + 14864.02 / 2(x / 26.35189)
M10B18 and M20B27 (white connector):
Coolant Temp Sensor Minimum Resistance: 102.4699 + 9511.018 / 2(x / 30.20366)
Coolant Temp Sensor Maximum Resistance: 256.4265 + 16548.04 / 2(x / 25.69821)
So I was poking through the Fuel System section of the E30 Bentley manual and noticed that the tables for testing the resistance of the coolant temperature sensor only contained 3 values (14 °F, 68 °F, and 176 °F). This skips a large range of ambient temperatures that the coolant could be at when testing the sensors, so I decided to use the values Bentley provided and generate a more comprehensive set of values. I plugged in the Bentley values into the mycurvefit website and generated equations using a Half-Life Exponential fitting method. In the equations below, the x variable refers to the coolant temperature in °F. Note that the equations are derived from the 14 °F, 68 °F, and 176 °F values provided in the Bentley, which states that a ± 2 °F margin of error for coolant temperature x is okay. Note that the E30 Bentley manual does not provide values for the M42 engine. The E36 Bentley manual shows the coolant temp sensor resistance values for the M42 that are the same as the ones for the M20B25 in the E30 Bentley manual. Based on that, I am going to go with the assumption that both use the same coolant temperature sensor.
M20B25 and M42B18 (blue connector):
Coolant Temp Sensor Minimum Resistance: 170.3153 + 11469.55 / 2(x / 27.21654)
Coolant Temp Sensor Maximum Resistance: 214.9207 + 14864.02 / 2(x / 26.35189)
M10B18 and M20B27 (white connector):
Coolant Temp Sensor Minimum Resistance: 102.4699 + 9511.018 / 2(x / 30.20366)
Coolant Temp Sensor Maximum Resistance: 256.4265 + 16548.04 / 2(x / 25.69821)
