Coolant temperature sensor (Mercedes-Benz C-Class W202)

Contents: Examination ↡ Installation ↡

The temperature sensor measures the coolant temperature and transmits the corresponding signals to the control device. The sensor contains an NTC element (NTC – negative temperature coefficient), which decreases its resistance as the temperature increases. If the sensor is faulty, the control device outputs a reserve value. This leads to the fact that the duration of the preliminary and subsequent heating is not maintained correctly.

1. 2.0L Engine: Remove the 6-pin plug from the heat control relay and measure the resistance between pin 6 on the plug and the housing (engine cylinder block). If the resistance tends to infinity, there is a break in the current-carrying line. If the resistance is below 1 Ohm, there is a short circuit in the electric line.

Specified value:

at 25°C: 2442 Ohm + 170 Ohm
at 80°C: 291 Ohm + 16 Ohm

2. 2.2/2.5L engine: Reduce the coolant pressure by removing the cap from the expansion tank filled with coolant.

3. Disconnect the plug (B 11/4) and unscrew the coolant temperature sensor.

4. Disconnect the plug (B 11/8x1) and unscrew the "coolant temperature sensor for subsequent heating" on the cylinder head.

Examination

1. Hang the thermometer in a water bath and heat it slowly.

2. Check the resistance of the temperature sensor with an ohmmeter. The measured value is OK if it is within the tolerance of + 5% (see table Temperature sensor resistance).

3. If the temperature sensor does not reach the specified values during measurements, it should be replaced.

Installation

1. Screw in the temperature sensor with a torque of 20 Nm.

2. Insert the cable plug (connector).

3. Fill with coolant.

4. Warm up the engine and check the coolant level.