HVAC systems rely on sensors to maintain their performance and efficiency. When these sensors fail, it can lead to uncomfortable indoor temperatures at best and damage or malfunction at worst. There are several different types of sensors, but if even one fails, your system will start to behave erratically.

Fortunately, detecting and diagnosing sensor issues is often straightforward, though ruling out other potential causes is still important. From temperature discrepancies to frequent cycling, recognizing the signs can help you resolve the issue sooner and in fewer steps.

At Heatwave Air Conditioning and Heating, we specialize in a variety of HVAC repairs, including sensor issues. In this blog, we’ve collected those insights into a guide to identifying and preventing common issues.

Types of HVAC Sensors

HVAC sensors are the sensory organs of your system, constantly monitoring various conditions to improve your comfort. Your system needs different types of sensors to measure different things; some measure temperature, while others measure humidity or airflow.

Here are the different types and how they function:

Temperature Sensors (HVAC Thermostat)

Your temperature sensor is more commonly known as a thermostat. These contain a material that changes resistance based on temperature. This change in resistance is converted into an electrical signal that your HVAC system interprets. When the temperature deviates, your system activates as needed.

Humidity Sensors

Humidity sensors monitor the moisture content in the air. They’re typically located in your system’s return duct or near the evaporator coil. These use technologies like capacitive, resistive, or piezoelectric sensors to detect changes in humidity.

The sensor converts these changes into an electrical signal, which your system interprets to control the dehumidification or humidification process.

Pressure Sensors

Pressure sensors, sometimes called manometers, measure air pressure within your HVAC system. They’re typically located in your ductwork, near the blower fan or the evaporator coil.

These sensors also use piezoelectric or capacitive technologies to detect changes in air pressure, which your system then interprets to regulate airflow and keep your system balanced. This helps prevent issues like uneven heating and cooling.

Symptoms of Sensor Failures in HVAC Systems

Precision is the bread and butter of your HVAC’s sensory system. If it produces incorrect data, the adjustments your system makes will be needless. Since there are multiple types of sensors, failure can manifest in different ways depending on the affected sensor.

Here are a few symptoms to look out for:

Temperature Sensor

Your thermostat displays temperatures that don’t match the actual room temperature.
Your system takes longer than usual to reach desired temperatures.
Your system turns off and on frequently.
Your system fails to turn on altogether.

Humidity Sensor

The air feels overly dry, leading to discomfort.
The air feels damp or stuffy.
Your system fails to activate the dehumidifier or humidifier when needed.
Your system cycles off and on, trying to correct humidity levels.

Pressure Sensor

Your system fails to start due to incorrect pressure readings.
Your system cycles due to inaccurate pressure information.
Low-pressure readings might prevent your blower from operating at full capacity.
High-pressure readings can cause your compressor to overheat and shut down.

Diagnosing Sensor Failures: Ruling Out Other HVAC Problems

The difficulty in recognizing sensor failures is that sometimes, other problems within your system manifest in similar ways. Issues like refrigerant leaks, clogged filters, or a malfunctioning compressor can all produce similar symptoms.

To rule out other hardware issues, a visual inspection can identify damage, disconnected wiring, or blocked vents. Other diagnostic tools like multimeters can test sensor readings against expected values, ensuring your sensors are functioning properly.

If your sensors check out, look to related components next. For example, problems with your control board can cause communication issues between sensors and your system. In this case, a replacement is sometimes in order.

What Causes HVAC Sensor Issues?

The most likely cause of your sensor issues is calibration drift over time. As sensors age, they can lose accuracy due to factors like extreme temperature fluctuations and neglect. If your system has physical damage, this can also affect sensor readings and cause erratic behavior.

Here are some other potential causes:

Contamination: Dust, dirt, or other debris can accumulate on your sensors, interfering with their operation.
Electrical issues: Faulty wiring, loose connections, or power surges can all damage sensors.
Extreme conditions: Sensors exposed to extreme cold or heat can malfunction.
Human error: Occasionally, sensors can be defunct from the factory, or accidental bumps or impacts can damage them.

HVAC Repair or Replacement for Faulty Sensors

Sensor issues don’t always demand replacements, but you might consider one if you want an upgrade. Whether a repair or replacement is more practical depends on the type of sensor, the nature of the malfunction, and the age of your system.

Temperature sensors are relatively simple components. If your issue is a malfunctioning digital display or a loose connection, repair is the better option. However, if your sensor itself is inaccurate or damaged, replacement is likely the only solution.

Once your humidity sensor fails or drifts out of calibration, you typically can’t restore it to its original accuracy through repair. Replacement also tends to be the more cost-effective option, as repairs might implicate other internal components.

If your pressure sensor fails, it’s often due to internal damage or calibration shifts. In most cases, attempting to repair your pressure sensor doesn’t guarantee restored accuracy or reliability, making replacement the best approach when dealing with inaccuracies.

HVAC Maintenance: Preventing Sensor Failures

HVAC maintenance for sensors involves a lot of checking and verifying. As dust and debris can interfere with readings, cleaning sensors and surrounding areas is often a good starting point.

Here are some other potential maintenance tasks:

Ensure sensors accurately reflect actual readings.
Inspect wires for loose connections.
Ensure sensors are in suitable locations.
Check sensor calibration using tools like hygrometers for humidity sensors.
Perform visual inspections of pressure sensors and surroundings.
Clean your system to prevent debris from reaching sensors and affecting performance.

Resolve Sensor Issues Quickly With Our HVAC Contractors

The HVAC contractors at Heatwave Air Conditioning and Heating can effectively differentiate sensor issues from other mimicking conditions within your system, ensuring accurate readings across all relevant metrics.

With our training and equipment, you can avoid prolonged discomfort and costly energy bills due to faulty sensors. Contact us today at (520) 623-1855 to get your HVAC system back on track.