Engine - Coolant Temperature Sensor/Switch: Description and Operation

Position
At cylinder head


Task
Detecting the coolant temperature and supplying information to the ME-SFI control module, and to control module of automatic A/C (N22) or air conditioning (N19), respectively.


Design
Metal housing with 2 separate NTC resistors 4-pin connector, diagonally different resistances.









Contact assignment at connector:
Contacts 1 and 4: ME-SFI control module
Contacts 2 and 3: control module of automatic air conditioning (N22) or air conditioning (N19).


Function
The NTC resistor integrated in the coolant temperature sensor (B11) alters its electrical resistance in line with the coolant temperature.NTC means Negative Temperature Coefficient in other words the electrical resistance becomes less as the temperature rises.

Example:
coolant temperature resistance
20 °C 2500 ohm ± 5%
80 °C 325 ohm ± 5%