Air Conditioning 101: What Does an AC Thermistor Do?

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Air conditioners are advancing, with many models using modern technology to provide energy-saving cooling effects, optimized efficiency, and smart device compatibility. These units are able to provide cold room temperatures, and adjust aircon operations according to the accurate readings on the thermistor.

In this article, we look into the importance of thermistors, and what they do in air conditioning systems. We also include common symptoms of a faulty thermistor, and how to check for a thermistor in need of a replacement!

What is an AC Thermistor?

An air conditioner thermistor is found on the majority of modern air conditioner models and units. It is a temperature sensor that detects the ambient temperature, which allows the air conditioning system to adjust the cold air coming from its vents through a resistance signal sent by the thermostat.

The thermistor is located near the evaporator coils, and reads the ambient temperature in the room to balance the cold air coming out of the air conditioner. The AC unit blows cold air into the room, the temperature sensor sends a reading to display the room temperature on the thermostat. There is a thermistor located outside the condenser unit as well for accuracy.

Thermistors come in two types: Negative Temperature Coefficient (NTC) Thermistor and Positive Temperature Coefficient (PTC) Thermistor - NTC thermistors being the more commonly-used thermistors in AC systems. These thermistors accurately read temperature changes, and the NTC thermistor decreases resistance as temperatures rise.

The Importance of AC Thermistors

1. Optimized Cooling Efficiency

The main purpose of an AC thermistor is for optimized cooling efficiency. As these temperature sensors read the ambient room temperature around the unit, it allows the thermostat to adjust the cold air blowing out of the air conditioner vents according to the room temperature reading.

This process keeps the room temperature at the desired setting, and factors in weather, humidity, and outdoor temperature in cooling the room, leading to a more comfortable cooling effect. The more accurate a thermistor, the more optimized the cooling efficiency of an air conditioning unit.

2. Energy-saving for Inverter Units

An air conditioner thermistor is especially useful in inverter models as these temperature sensors detect changes in room temperature, allowing the AC unit to optimize its cooling efficiency for energy-saving purposes.

With inverter units, the speed of the compressor is controlled according to the temperature reading on the thermostat. Once the room has reached the desired temperature set on the thermostat, the compressor motor lowers in speed to conserve energy consumption. The thermistor is what sends the room reading to the thermostat to activate this process.

Diagnosing a Faulty Aircon Thermistor

#1 Inaccurate Temperature Sensors

An aircon thermistor is not the same as a thermostat. The thermistor is more complex, and provides accurate temperature readings that the thermostat cannot do alone. A faulty thermistor, however, can no longer read the room temperature as conductivity varies, processing inaccurate temperature readings.

When this happens, you may notice the temperature displayed on your unit fluctuate between various ranges. You may also notice the room temperature reading much higher or lower than the actual room temperature. A Luce Aircon technician may offer corrective measures to fix the problem.

#2 Faulty Thermistor Cable

Another symptom of a faulty thermistor is your AC unit blowing cold air at intervals. Short bursts of cold air, followed by periods of warmer air, is a sign of a problem with your unit, which may take root at the thermistor. However, because this can be a symptom of various faulty aircon parts, you cannot determine if the problem lies with the thermistor immediately.

Testing your thermistor cable is a surefire way to find out if the part is faulty. Conductivity relies on the movement of electrons in heated metal, and thermistors use this principle to conduct temperature readings. Testing the cable is based on the same principle:

  1. Use a multimeter on your thermistor.
  2. Take note of the current reading your thermistor is providing.
  3. Change the resistance value to the rated resistance value. This will determine whether your thermistor is working at peak condition. If you are unable to set the value to the rated resistance value, then it means your thermistor is faulty.
  4. Alternatively, you can use a heating tool such as a hair dryer to watch for temperature changes read by your thermistor. Thermistors can detect even slight changes in temperature, so it should be able to detect a sudden increase in temperature immediately.

Keeping Up with Your Air Conditioners

Modern air conditioning systems have come a long way from traditional and outdated cooling systems. Manufacturers have made improvements in coolant, compressors, and temperature sensors that optimize the cooling effects of air conditioners. Keeping up to date with your air conditioner maintenance is the way to ensure your unit is working properly.

When scouting for a reliable air conditioning service, look for a company that knows how to handle your unit. At Luce Aircon, our HVAC professionals have the technical knowledge to clean, assess, and repair various air conditioner units and models across different brands. You know your AC unit is in good hands when you get Luce Aircon services!

Got aircon thermistor problems? Give us a call today, and one of our technicians can check on your air conditioning system!

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