VW Passat - coolant temperature display

In the case of the above-mentioned vehicle type, the coolant temperature may fluctuate considerably according to the display in the instrument cluster. An error memory entry indicating a defect in the engine cooling system is not present. If the above-mentioned fault arises and no definite faults have been found in the periphery of the affected systems during troubleshooting, particular attention should be paid to the sensor for the coolant temperature.

This sensor is installed in the engine coolant circuit. It utilises the temperature dependence of materials with negative temperature coefficients (NTC). This means that the resistance of the sensor decreases as the temperature rises. A defective coolant temperature sensor can cause various problems. Difficulties starting the engine, increased idle speed and poor exhaust gas values can all also occur if the sensor is defective.

In the course of further troubleshooting, the temperature sensor should be checked using a suitable diagnostic device on the basis of the parameter query. If abnormalities are detected here, replacing the sensor can remedy the problem. Anomalies that indicate a defective sensor are, for example, that the engine temperature value remains static, jumps back and forth or is not plausible in relation to the actual engine temperature.

Once the cause of the fault has been rectified, delete the error memory and then carry out a test drive.

Repair and maintenance work on the cooling system must be carried out in accordance with the manufacturer's instructions. Some manufacturers stipulate special venting routines that must be adhered to.