BMW 13621703993 Double Temperature Switch

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As the temperature increases, the electrical resistance of the sensor decreases. The Engine Control Module (ECM) constantly monitors the value received from the ECT sensor to determine the engine's fuel mixture requirements.

The ECM adjusts ignition timing and air/fuel mixture based on the coolant temperature, receiving a 5-volt reference voltage. The voltage drop across the sensor changes according to the coolant temperature.

When removing and installing the sensor, caution should be taken to avoid spraying hot engine coolant. The sensor should be tightened to the specified torque, and the cooling system should be topped off and bled.

The engine coolant temperature gauge uses a heat-sensitive sending unit to transmit an electrical signal to the gauge. The sending unit is a heat-sensitive variable resistor located on or near the cylinder head and threads into an engine coolant passage.

First, unplug the sensor and measure the coolant temperature as close as possible to the sensor location. Then, measure the resistance between the terminals of the sensor and compare the results to a chart. With the ignition switch ON, the sensor should receive 5 volts at one of the connector terminals. The other terminal is the return signal to the control unit and should not be used for voltmeter ground.

The ECT sensor, also known as the dual temperature sensor, signals coolant temperature to the DME system and the instrument cluster temperature gauge.