The evaporator temperature sensor is one of the control devices found in automotive air conditioning systems. It’s a negative temperature coefficient thermistor. It changes resistance according to temperature changes in the evaporator core.
What’s the function of the evaporator temperature sensor?
The evaporator temperature sensor tells the PCM or ECM the temperature of the evaporator and keeps the evaporator core from freezing .It is usually located inside the hvac case underneath the dash, mounted on the evaporator core. The evaporator temperature sensor acts as a protection device maintaining the evaporator temperature between 34º F and 37º F. These limits could vary depending on the ambient temperature in Automatic temperature control systems.
When the temperature drops bellow a preset temperature value the compressor magnetic clutch will be turned off, thus stopping the compressor and avoiding damage to it, due to the change in oil viscosity and poor lubrication back to the hvac compressor, because of too low temperature in the system.
What are the symptoms of a bad evaporator temperature sensor?
This sensor could fail in several ways and sometimes will set a code that could be check with a scan tool. This code will reset automatically after replacing the sensor or in some cases a scan tool will be needed for this purpose. A problem with the evaporator temperature sensor will disable the ac system preventing the compressor from running and blowing ambient temperature air from the ac vents.
Types of evaporator temperature sensors.
Thermostatic switches are created in different ways. One popular method utilizes a metal disk that’s bent into the shape of a bowl .As the switch heats or cools, the shape of the bowl changes activating or deactivating the ac compressor. Another type of thermostatic utilizes a bulb, a capillary tube, and a bellows. The bulb and capillary tube are filled with refrigerant, oil or alcohol. As the temperature changes, the liquid expands or contracts, causing the bellows to move triggering the electric contacts
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An incorrect understanding or approach to the air conditioning electronic diagnosis could lead you to waste time and money replacing unnecessary components in the ac system. Auto A/C Repair, specializes on automotive hvac systems only. Give us a call today at (786) 483-9406.We offer on-site free estimates and check ups.