Why is my aircon not cold?

There can be a lot of reasons why your air conditioner is not cold. And you may require an aircon technician to check on this to find out the exact reason. In this article, we will explore nine reasons why your aircon is not cold. We will also discuss steps for troubleshooting this issue. A separate section will be created for aircon users whose aircon is not cold only in one room. In addition, we will talk about  how different brands affect the coldness level of the unit plus the estimated cost of fixing this issue. Lastly, we will explain how an air conditioning unit not being cold affects your electricity bill.

If your air conditioner is running but not cooling effectively, it could be due to several underlying issues. Here are nine common reasons why your aircon might not be blowing cold air, along with detailed explanations:

Aircon Blinking Lights

Blinking lights on your aircon unit often indicate an error or fault in the system. Modern air conditioners are equipped with diagnostic systems called error codes that, in some aircon models, use blinking patterns to signal specific problems. These issues could range from electrical faults, sensor malfunctions, or even a failing compressor. Refer to your user manual to decode the blinking pattern or call a professional technician to diagnose and resolve the issue. If your aircon light is blinking, that means that there is an error with the unit. The blinking light will reflect an error code. For example, the number of times a Mitsubishi aircon blinks will indicate a particular error. 7 times usually means that the PCB is malfunctioning. Hence, if there is an error in the system, it will likely shut down to prevent further damage.

Low Aircon Gas Level

Refrigerant is the substance responsible for absorbing heat from your room and releasing it outside. So, if your aircon is low on refrigerant, it won’t be able to cool the air effectively. Low refrigerant levels are often caused by leaks in the system. A professional technician can locate the gas leak, repair it, and recharge the refrigerant to restore optimal cooling performance. If your aircon gas level is insufficient, your aircon may not be cold enough or it may be totally not cold at all. That is because the aircon unit requires a sufficient pressure level for the blower wheel to blow out cold air. In some aircon brands such as Daikin Aircon, the air conditioning system will simply cease working. It will result in your aircon blinking instead. However, for a non-inverter aircon, there may not be a blinking light to indicate low refrigerant levels.

Dirty Evaporator Coil 

The evaporator coil, located inside the indoor unit, absorbs heat from the air. Over time, dust and debris can accumulate on the coil, reducing its ability to absorb heat. This can lead to poor cooling performance and even cause the unit to freeze up. Regular cleaning and maintenance of the evaporator coil are essential to ensure efficient operation. Other than insufficient gas levels, this is actually the most common reason why your aircon is not blowing cold air. A dirty evaporator coil will make the fan coil unit inefficient in receiving the cold air. It will “clog up” the fan coil unit, hence the cold air will not be transferred to the blower efficiently. If the evaporator coil is extremely dirty, your unit will need an aircon chemical overhaul because aircon normal servicing will not suffice.

Compressor Not Working

The compressor is the heart of your air conditioning system, responsible for circulating refrigerant and maintaining the cooling cycle. If the compressor fails, the refrigerant cannot flow properly, and your aircon will not cool the air. Compressor issues can be caused by electrical problems, overheating, or wear and tear. A professional inspection is necessary to determine if the compressor needs repair or replacement. In most cases your fan coil unit will be indicating this problem through blinking lights. For certain aircon brands, however, no error code is displayed.

Aircon Thermistor Malfunctioning

The thermistor is a sensor that measures the temperature of the air entering the aircon unit. If the thermistor malfunctions, it can send incorrect signals to the control board, causing the aircon to run inefficiently or not cool at all. A faulty thermistor may need to be recalibrated or replaced to restore proper functionality. So, if your aircon is cold for some time and it turns off by itself followed by blinking lights, it is possible that the  thermistor is malfunctioning. The thermistor’s resistance value is actually the basis for the system ‘telling’ the compressor to work harder or less hard, all of which determines the amount of cold air supplied to the fan coil unit.

Dirty Blower Wheel 

The blower wheel is responsible for circulating air through the aircon unit and into your room. If the blower wheel becomes clogged with dirt and debris, it can restrict airflow, reducing the unit’s cooling capacity. Cleaning the blower wheel during routine maintenance can help maintain optimal airflow and cooling performance. Most issues caused by a dirty blower wheel or a dirty evaporator coil can be resolved by  routine aircon servicing. However, not all forms of aircon servicing can solve the dirty blower wheel issue. For example, if your aircon technician only vacuums the evaporator coil without brushing the blower wheel, your blower wheel may still be dirty. And a dirty aircon blower wheel will still prevent cold air from blowing out efficiently.

Malfunctioning Parts

Various components within your air conditioning system, such as the aircon capacitor, fan motor, or control board, can malfunction over time. These parts are critical to the proper operation of the system, and any failure can lead to reduced cooling efficiency. Regular servicing can help identify and replace worn-out aircon parts before they cause significant issues. So, other than the aircon thermistor, there are several other parts that can cause your unit to not blow cold air. For example, your aircon may have a broken fan blade in the outdoor condenser unit. A broken fan blade in the outdoor unit will cause the hot air outside to not disperse properly, resulting in an overheated compressor and lack of cold air from the unit. The aircon PCB and fan motor are the two components most susceptible to failure. Once broken, they will cause the system to stop functioning and hence no cold air comes out of the aircon.

Insufficient BTU

The cooling capacity of an aircon is measured in BTUs. If your aircon unit has insufficient BTU for the size of the room, it will struggle to cool the space effectively. For example, a small unit in a large room will run continuously without reaching the desired temperature. This is why it is important to make sure your aircon’s BTU rating matches the room size for optimal performance. Take, for instance, how you tend to require different temperature settings to achieve a similar cooling level when you turn on your aircon at different time periods. That is because the outdoor temperature level affects the coolness of your unit. If the outdoor temperature is very high, the condenser unit will have to work harder to supply the same amount of cold air to the fan coil unit. Similarly, the BTU of your aircon unit may be enough during colder periods but not when the temperatures are soaring. The BTU may not be sufficient as there are extra heat sources that your aircon will have to compensate for, and this results in a situation in which your aircon is not cold.

Compressor Overheating

The compressor can overheat due to prolonged use, lack of maintenance, or insufficient refrigerant levels. Overheating can cause the compressor to shut down as a safety measure, leading to a loss of cooling. To prevent this, ensure your aircon is serviced regularly, and avoid running it continuously for extended periods. If your aircon condenser unit is very dirty, it will close up the fins of the condenser unit and the hot air venting through the compressor will not be able to disperse fully. Hence this will result in an overheated compressor. An easy way to solve this problem is to do a chemical wash on the compressor unit.

Lesser known causes of an aircon failing to blow cold air and how to address them