Checking the coolant level sensor (Mercedes-Benz Sprinter 903)

There is a coolant level sensor in the expansion tank. This device does not relieve you from the need to regularly check the level, but it is very helpful in case of a sudden drop, for example during a trip.

When the ignition is on and the engine is not running, the indicator lamp in the instrument cluster lights up at half brightness. If the coolant level is normal, the lamp goes out when the engine is started; if there is not enough coolant, on the contrary, it lights up brighter.

The control lamp is connected to a sensor in the expansion tank, the contact of which is closed by the float. If there is no liquid, the contact opens.

If the indicator lamp does not light at all when the ignition is on, it may have burned out.

If the lamp continues to light when the engine is running and the coolant level is normal, the sensor is faulty. In this case, when the plug is disconnected from the sensor, the lamp goes out. It is necessary to remove the sensor, check the float movement and the connector contact. Replace the sensor if necessary.

Material borrowed from an online resource (MERCEDESMAN)