May 21, 2024

What is the Purpose of an Evaporator Temperature Sensor?


The evaporator temperature sensor is crucial for monitoring the temperature of the evaporator, which is essential for cooling the refrigerant in the HVAC system. These sensors are vital in preventing the evaporator from freezing, which could result in damages and hinder the system’s ability to effectively control cabin temperature. Positioned close to the evaporator coil within the air conditioning unit its main role is to supervise the air temperature as it passes through the evaporator to ensure it stays at a level.

A functioning evaporator temperature sensor plays a role in maintaining a vehicles air conditioning system efficiency by preventing freezing of the evaporator, which could cause significant harm to the system. If not working correctly this sensor can lead to reduced cooling effectiveness potentially causing freezing of the evaporator and further harm. While it may not impact a vehicles safety or dependability directly a faulty sensor can notably decrease cabin comfort. This underscores how important it is to select an evaporator temperature sensor and comprehend its uses and technical specifications, for performance of the AC system.

Understanding Evaporator Temperature Sensors

The evaporator temperature sensor is a part of a cars air conditioning system helping to keep the HVAC system running. It detects the temperature of the evaporator core, which is essential, for cooling the refrigerant. This measurement is important as it prevents the evaporator core, from freezing and ensures that the system works effectively without any harm.

Key Functions:

  • Overcooling and Overheating Protection: It prevents the evaporator from getting too cold or too hot, safeguarding against system damage.
  • Fan Speed Control: Assists in controlling the speed of the indoor fan motor, enhancing comfort levels within the vehicle.
  • Outdoor Defrosting: Plays a role in the outdoor defrosting process during heating operations, maintaining optimal performance.

Sensor Types and Measurement:

  • Types: The sensors can be thermistors, thermocouples, or Resistance Temperature Detectors (RTDs), each varying in their method of temperature measurement.
  • Measurement Process: They detect temperature changes and transmit this data to the control system, which then adjusts the compressor’s operation to maintain desired temperature levels.

Symptoms of a Faulty Sensor:

  • Inconsistent cooling performance.
  • Frequent AC cycling.
  • Unusual frost or ice build-up.

Regular vehicle maintenance is essential for ensuring the evaporator temperature sensor functions correctly, preventing costly damages and maintaining optimal AC performance.

Key Features of Evaporator Temperature Sensors

Evaporator temperature sensors are carefully designed to deliver performance, in situations. These sensors possess a variety of characteristics that are essential for use, in HVAC systems and other applications that demand precise temperature monitoring.

Accuracy and Stability:

  • High accuracy and long-term stability ensure precise temperature measurements, crucial for the optimal function of HVAC systems.
  • Response Time: Capable of detecting rapid changes in temperature, these sensors have a response time of 10 seconds from 60°C oil to 20°C oil, facilitating timely adjustments to the system.

Design and Durability:

  • Their small size and flexible packaging allow for straightforward installation in diverse systems.
  • The sensors are designed with a snap-fit housing and an easy twist-to-lock design, minimizing the risk of wiring insulation damage and simplifying the installation and service process.
  • Tested for durability, they have passed a 2000-hour submersion test, underscoring their reliability.

Variability for Applications:

  • Available in pigtail and fin-type versions, these sensors cater to different application requirements.
  • They offer alternate RvT curves and come in various geometries to meet specific package requirements, ensuring compatibility across a wide range of systems.

Technical Specifications

Precise and durable temperature monitoring plays a role, in avoiding the freezing of the evaporator core, a key element for ensuring HVAC systems effectively regulate cabin temperature. The detailed requirements, for evaporator temperature sensors emphasize their accuracy and dependability across scenarios;

Temperature Measurement Accuracy and Range:

  • Operating temperature range: -40 to 85°C
  • Storage temperature range: -40 to 90°C
  • Temperature accuracy: ±0.20°C at 0°C and ±0.40°C at 25°C

Sensor Details:

  • NTC part number: NDUS7655
  • Housing material: Nylon 6/6
  • Weight: 4.9 gr.
  • Connector type: Packard Electric 150 series
  • Mating connector: Packard Electric 12047662
  • Temperature coefficient: 3988K (25/100)

Sensor Types and Performance:

  • Thermocouples: Common, least expensive, with typical accuracies of 1-2°F but limited operating range.
  • Semiconductor devices: Low-cost, output voltage/current proportional to temperature, comparable accuracy to thermocouples.
  • RTDs: Offer higher accuracy than thermocouples, limited operating range.
  • Thermistors: Provide very high accuracy (down to 0.01°C) over a limited temperature range.

This detailed summary helps users choose the evaporator temperature sensor, for their HVAC system needs ensuring top notch performance and dependability.

Installation and Service

Setting up and maintaining the evaporator temperature sensor is crucial to ensure that HVAC systems operate efficiently and effectively. Here are the essential steps involved in this process:

Location and Diagnosis:

The sensor is usually positioned in front of where the air flows out from the evaporator or connected to the part of the evaporator fins. If you suspect a sensor a Heating AC Inspection, which includes diagnosing the sensor can cost, between $145.99 and $170.00 in USA.

Some usual indicators of a failing sensor are cooling the air conditioner not shutting off at the desired temperature and increased utility costs.

Testing and Replacement:

To check the sensor grab a multimeter. Set it to measure ohms or resistance. Then immerse the sensor, in water. See if the resistance shifts, showing that its working correctly.

When swapping out the sensor first turn off the power take off the access panel, unscrew the sensor put in the one and make sure there’s a clear connection using a multimeter before turning the power back on.

Maintenance and Troubleshooting:

Regular checks for signs of wear or damage are essential. Cleaning or replacing the sensor might be necessary if it’s not functioning correctly.

Addressing common issues involves sensor replacement, wiring repairs, cleaning the sensor, refrigerant recharge, and tackling corrosion.

Proper installation and regular service ensure the evaporator temperature sensor operates efficiently, preventing abrupt temperature changes and discomfort.

Applications and Use Cases

Evaporator temperature sensors play a role in a range of scenarios helping devices function effectively and securely in diverse situations. Here we outline the purposes and practical uses of these sensors;

HVAC Systems:

  • Cooling: Prevents the evaporator coil from dropping below a specified temperature, safeguarding against overcooling.
  • Heating: Protects against overheating and freezing by shutting down the compressor if temperatures fall outside safe parameters.
  • Fan Speed Control: Assists in regulating the speed of the indoor fan motor, optimizing comfort levels.
  • Outdoor Defrosting: Aids in defrosting outdoor units to maintain performance.

Automotive Applications:

  • Climate Control: Contributes to maintaining the vehicle’s internal climate, enhancing passenger comfort.
  • Preventing Frost Buildup: Helps avoid system icing that could impair performance.
  • Model Compatibility: Fits specific models, e.g., 2013 Nissan 370Z and Altima variants, indicating its adaptability across different automotive systems.

Specialized Equipment:

  • Air Handling Units (AHUs): Measures air temperature post-cooling coil, maintaining desired temperature and humidity levels.
  • Chillers: Monitors chilled water temperature, ensuring efficient operation and temperature regulation.
  • Symptom Detection: Identifies issues like irregular cooling and frequent AC cycling, signaling the need for sensor inspection or replacement.

This comprehensive utilization underscores the evaporator temperature sensor’s critical role in maintaining system performance and efficiency across a spectrum of applications.

Choosing the Right Evaporator Temperature Sensor

Selecting the right evaporator temperature sensor involves considering various factors to ensure optimal performance and reliability in HVACR systems. Key considerations include:

Symptoms of a Bad or Failing Sensor:

  • No cold air from the AC system.
  • Temperature fluctuations.
  • The AC compressor not activating.

Critical Selection Criteria:

  • Accuracy: Essential for maintaining the desired temperature. The choice of sensor type (thermistors, thermocouples, RTDs) depends on the temperatures most often recorded.
  • Application Requirements: Consider the temperature range, accuracy, robustness, and cost. The medium (e.g., water, air, gas) and installation location (e.g., air conditioning systems, engines) also influence the selection.
  • Sensor Characteristics: Factors such as accuracy, range, reliability, repeatability, and output type are crucial. Sensors must withstand harsh conditions.
  • Communication Protocols: BACnet, MODBUS, and TCP/IP are necessary for remote monitoring, control, and maintenance.

Specific Sensor Details:

  • SKU #AA0001, ITEM #NTK75929, BRAND NTK.
  • Connector Shape: Rectangular.
  • Mounting Type: Push On.
  • Terminal Quantity: 2.
  • Terminal Type: Blade.
  • Includes Mounting Hardware: No.
  • Warranty: 3 Years/36K Miles.

Understanding these factors ensures the selection of an evaporator temperature sensor that meets the specific needs of HVACR systems, enhancing system performance and reliability.


In our, in depth exploration we’ve highlighted the importance and complex functions of the evaporator temperature sensor in HVAC systems in cars. We’ve stressed the significance of temperature monitoring to prevent issues like evaporator core freezing well as discussed the impact of sensor malfunctions on cabin comfort though not directly on vehicle safety. We’ve delved into sensor types their attributes, technical details and selection guidelines to lay a solid foundation for choosing the right sensor for optimal HVAC system performance.

Moreover our examination of installation methods, service procedures and diverse applications showcases how the sensor plays a role in maintaining system efficiency and reliability across scenarios. This narrative underscores not the need for maintenance and selecting appropriate sensors based on specific HVAC system needs but also hints at potential advancements in sensor technology through further research. As technology progresses so will the capabilities and uses of evaporator temperature sensors underlining their role, in ensuring HVAC system operation and enhancing comfort levels and performance standards.

1 thought on “What is the Purpose of an Evaporator Temperature Sensor?

  1. I do not even know how I ended up here but I thought this post was great I dont know who you are but definitely youre going to a famous blogger if you arent already Cheers.

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