Mercedes of the S-class W202

1993-2000 of release

Repair and operation of the car

Mercedes W202
+ 1.2. General information
+ 2. Maintenance
+ 3. Engines
+ 4. Lubrication system
+ 5. Cooling system
+ 6. Heating, ventilation
+ 7. System of ignition
- 8. Fuel system
   + 8.1.1. Introduction
   - 8.2. System of injection of petrol engines Principle of work of PMS Principle of work of HFM
      8.2.2. Self-diagnosing of a condition of system of ignition and injection of fuel
      8.2.3. Air flowmeter
      8.2.4. Thermal sensor of cooling liquid
      8.2.5. The sensor of the soaked-up air
      8.2.6. System of vacuum pipelines
      8.2.7. The fuel distributor with valvate nozzles
      8.2.8. Valvate nozzles
      8.2.9. Oxygen sensor (lambda probe)
      8.2.10. Diagnostics of malfunctions of system of injection of gasoline
      8.2.11. What should be known to the owner of the car with the injector engine
      8.2.12. Turbo doctor
   + 8.3. System of injection and power supply of diesel engines
   + 8.4. System of production of exhaust gases
+ 9. Transmission
+ 10. Running gear
+ 11. Steering
+ 12. Brake system
+ 13. Body
+ 14. Electric equipment
+ 14.2. Electrical circuitries

8.2.4. Thermal sensor of cooling liquid


The thermal sensor takes temperature to cooling liquid and transmits electric signals to the actuation device. The sensor is equipped with a NTC element (NTC – negative temperature coefficient) which reduces the resistance at increase in temperature. At malfunction of the sensor the actuation device chooses the equivalent size which corresponds to temperature of cooling liquid at the engine heated to working temperature. At low external temperatures and the cold engine it leads to difficulties at launch of the engine and to its work out of the modes.

The thermal sensor is in the thermostat case.


1. Reduce pressure in a contour of cooling liquid. For this purpose open a cover of a compensation tank with cooling liquid.
2. Remove the protection cover (5/3) from the thermostat case.
3. Remove the shtekkerny socket and unscrew the thermal sensor (B11/3).


1. Suspend the thermal sensor in a water bath and slowly heat it.
2. Check an ohmmeter thermal sensor resistance. The measured value is considered normal if it is in the admission of 5% (see the table Thermal Sensor Resistance).
3. If at measurements the thermal sensor does not reach preset values, it should be replaced.


1. Screw in the thermal sensor with a new sealing ring and tighten with the moment 20 N. of m.
2. Spread the shtekkerny socket of a wire.
3. Warm up the engine and check tightness of connections. Double-check the level of cooling liquid.

Thermal sensor resistance

+20 °C
apprx. 2500 Ohms
+30 °C
apprx. 1700 Ohms
+40 °C
apprx. 1170 Ohms
+50 °C
apprx. 830 Ohms
+60 °C
apprx. 600 Ohms
+70 °C
apprx. 435 Ohms
+80 °C
apprx. 325 Ohms
+90 °C
apprx. 245 Ohms
+100 °C
apprx. 185 Ohms