When your facility’s climate control starts acting up, the thermostat or compressor is not always at fault. The issue might be with a small but vital component: the AC sensor. Whether you’re a business owner or operations manager, disruptions caused by inaccurate temperature control can lead to unnecessary downtime or complaints from tenants and staff.

Let’s explore how AC sensors work, why they fail, and how to tell when it’s time for an AC sensor replacement. Understanding how these components behave helps you take corrective action early and avoid bigger problems.

What Is an AC Sensor and What Does It Do?

AC sensors are temperature-sensitive components that help control when your air conditioning system turns on or off. They read the air temperature as it passes over the evaporator coil and signal the compressor to activate or shut down based on the thermostat setting. 

This temperature feedback loop keeps indoor environments stable. When the sensor fails, the system may overcool the space, run inefficiently, or cause coil freezing. This is why many systems rely on multiple sensors, especially in commercial or larger residential setups. Each monitors key points like discharge air, humidity, suction line, and return bend.

When and Why AC Sensors Can Fail

AC sensors don’t fail without a reason. Their performance can break down due to several conditions. Below are the most common failure points that affect sensor reliability and overall HVAC performance. 

Physical Deterioration

Over time, sensor wires can become brittle or frayed, especially in older units. Repeated vibration and thermal cycling may cause the sensor to shift out of position, bending it away from the optimal airflow path.

Once displaced, the sensor can no longer take accurate temperature readings, and the system may begin cooling erratically or shut down unexpectedly.

Electrical Issues

Sensors connect directly to the control board. If leads become corroded or the wiring is installed loosely, the electrical signal may drop intermittently. This could result in false readings, causing the unit to cycle at the wrong times or refuse to start.

In some cases, damage may also stem from improper installation or a weak connection built into the sensor during manufacturing.

Environmental Stress

Moisture from evaporator coil condensation can corrode terminals, especially in systems with poor drainage or limited air movement. In cold climates or during shoulder seasons, freeze-thaw cycles can also crack plastic housings. These conditions weaken the sensor’s ability to maintain accuracy.

Accidental Damage

Even during routine coil cleanings or filter replacements, sensors can be bumped or partially dislodged. Without careful inspection after service, these disturbances go unnoticed until temperature problems arise.

Power Surges or System Cycling Issues

Fluctuations in voltage during power outages or grid instability can damage electronic components. Similarly, frequent short cycling, which is often caused by thermostat placement or sizing errors, adds wear and tear that degrades the sensor faster than usual.

4 Signs You Need an AC Sensor Replacement

Many sensor issues don’t appear suddenly. Instead, they often appear as minor performance problems that worsen over time. Knowing what to look for can help you act before minor symptoms become larger system failures. 

Here are four common signs that point to a failing sensor: 

• Inconsistent Temperatures: If your indoor space feels cooler or warmer than the thermostat reads, the sensor may misread the airflow temperature. This can cause discomfort and make the system work harder to stabilize conditions.

• Short Cycling: When a sensor provides faulty or incomplete readings, the compressor may turn on and off too frequently. This short cycling strains system components, raises energy usage, and increases the risk of long-term damage. 

• AC Won’t Start or Runs Non-Stop: A sensor reading temperatures inaccurately (or not at all) can cause the system to run constantly or fail to start entirely. Sometimes, the unit might keep blowing cool air even after the set temperature is reached. This can lead to frozen coils and wasted electricity. 

• Higher Than Usual Monthly Utility Bills: If your energy costs are spiking without an apparent cause, the sensor might be over-activating the compressor. This inefficiency is often overlooked but indicates that something in the control sequence is malfunctioning. 

If one or more of these signs appear, it’s time to consider an AC sensor replacement. Swapping out a worn sensor restores accurate readings and prevents further strain on your system. 

Seeing the Signs? It’s Time To Reset Your System’s Control

 

AC sensors may be small, but they can throw the entire system off balance when they fail. If you see signs like erratic cycling or unexplained energy spikes, take action before their performance slips further. Early diagnostics and timely AC sensor replacement can prevent larger problems and reduce operating costs. 

At Value Controls, we carry new and certified pre-owned HVAC parts, including hard-to-find models no longer available through OEMs. Explore our inventory today and get the replacement you need to keep your system running reliably.   

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AC Sensor

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