Here's a breakdown of their individual functions and how they interact:
Engine Coolant Sending Unit:
* Function: The sending unit is a simple switch that detects when the engine coolant reaches a specific temperature threshold (usually around 212°F).
* Signal: When the coolant reaches that temperature, the switch closes and sends a signal to the dashboard gauge.
* Result: This signal activates the "hot" indicator on the gauge, alerting the driver to a potential overheating issue.
Engine Coolant Temperature Sensor (ECT):
* Function: The temperature sensor is a resistor that changes its resistance based on the temperature of the coolant.
* Signal: The ECT sends a variable voltage signal to the engine control unit (ECU).
* Result: The ECU uses this signal to determine the actual engine temperature. This information is used to:
* Control the cooling fan: The ECU will activate the fan when the coolant temperature exceeds a setpoint to cool the engine down.
* Adjust fuel mixture: The ECU will adjust the air/fuel ratio to compensate for temperature changes and ensure optimal engine performance.
* Monitor the engine: The ECU will monitor the temperature readings and trigger warning lights or codes if it detects abnormal temperature fluctuations.
How They Work Together:
* The sending unit provides a basic warning system to alert the driver about potentially overheating conditions.
* The ECT provides precise temperature readings to the ECU, which allows for more accurate engine control and performance management.
In essence, the sending unit acts as a simple alarm system while the ECT provides detailed temperature data for the ECU to use. Together, they ensure proper engine temperature control and prevent damage caused by overheating.
Important Note: Some vehicles may only have one sensor that acts as both a sending unit and a temperature sensor. In these cases, the sensor performs both functions simultaneously.
