Top 7 Reasons Why Your Mini Split Is Not Blowing Cold Air

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Few things can be worse than a malfunctioned air conditioner in the sweltering summer heat. Just a few hours without the cooling effect of the AC can feel like a year in hell.

We strongly recommend that you call an HVAC technician to diagnose and rectify the issues. However, it always helps to know what could go wrong to prevent the issue where possible.

Moreover, sometimes an air conditioner may fail to blow cold air for fundamental reasons such as wrong thermostat settings – an issue you can fix without a technician’s help.

Mini Split Not Blowing Cold Air (7 Common Causes and Solutions)

The following are seven of the most common reasons your air conditioner may fail to generate cold air or generate air that’s not as cold as you’d like.

1. Power Issues

It might sound basic, but sometimes the lack of cold air may result from a power issue. For example, maybe the air conditioner is unplugged. Or perhaps the power cord is loosely attached. Where this is the case, it will not run even when you switch it on.

Another possibility is a blown a fuse or tripped circuit breaker. All air conditioners have a fuse or breaker to protect the appliance from power surges. If the breaker trips or the fuse blows, the air conditioner won’t run. It’s wise to check for such issues before looking for more complex AC malfunction causes.

Solution: Begin by ensuring that you have power and the AC is plugged in properly. Also, make sure that the connecting wires are in good condition and attached snugly. If everything is fine, check to ensure that the fuse hasn’t blown or the breaker tripped.    

2. Thermostat Issues

If you find no issues with power, the next place to check is the thermostat. Two things are possible here. First, the thermostat might be set wrongly. Perhaps you set it to 70˚F when you meant to set it at 78˚F. Or, maybe you set it correctly, but someone later tampered with the setting.

Alternatively, you might be dealing with a malfunctioned thermostat. If the thermostat is broken, it can easily jump to a different setting a few seconds after setting it to a specific temperature. Broken thermostats may also fail to pick up on temperature drops when set to “Auto Mode.”

Solution: You’re allowed to attempt to repair the thermostat. Check all the wires to ensure that power is reaching the thermostat. Perhaps you need to replace the battery? Also, observe it for a few seconds to confirm that it picks up temperature changes accurately and doesn’t jump values. If all your efforts are in vain, consider buying a new thermostat. They cost around $20.

3. Is it a Clogged Filter?

Clogged filters can significantly compromise cooling efficiency. First off, whenever the filter is clogged, airflow is restricted. Since cool air must pass through the filter before re-entering the house, the constricted airflow can result in insufficient cooling output.

Problems may also arise if the AC has a mechanism to automatically turn off the AC if the filters are completely blocked. This helps prevent overheating that may damage the internal components of the air conditioner. Overheating is particularly bad for the motor.

Solution: Regular maintenance is the best solution here. Don’t wait for the motor to clog. Instead, clean the AC regularly, in line with the manufacturer’s recommendations. Most manufacturers recommend cleaning the filters at least once every two weeks and replacing them once every 1-2 months.

4. Ice Build-Up

Ice build-up is a condition that occurs when the evaporator coils become too cold. This often results in the moisture in the vicinity of the coils condensing onto the coil and freezing. Signs of ice build-up include a suspiciously hot compressor. The compressor may even ice up or burn out. 

Different issues can cause ice build-up. If the blower isn’t working, the coolant may fail to warm properly, resulting in freezing. A dirty filter can also decrease airflow across the coil, resulting in freezing. Faulty metering devices and an oversize AC system can also cause evaporator coil freezing.

Solution: If you suspect ice-build-up, the first step is to turn off the air conditioner and let the ice melt away. After that, try to identify and fix the problem. Cleaning the filters and clearing debris build-up in and around the compressor can help. Then, call an HVAC technician.

5. Dirty Condenser

The condenser unit which sits outside the house can also have a blockage. Think about it. The unit sits outside the house all year round. How much dirt would it possibly gather over that period?

What about leaves and twigs? Although manufactures attempt to prevent excess accumulation of debris, it’s impossible to go a whole year without at least a few particles entering the outdoor unit.

The ice build-up issue mentioned above is one of the first signs that you may have a dirty condenser. Low cooling output or complete lack of cooling can be another sign. You may also notice that the AC struggles to get going.

Solution: Regular maintenance can resolve most condenser blockage issues. Every few weeks, walk around the area to make sure that it’s clear of pebbles and debris. Also, trim the grass around the area. It’s also necessary to open the unit and dust off the internal components once in a while.  

6. Clogged Drain System

Air conditioners are also supplementary dehumidifiers. In addition to removing excess heat from your home, they also extract moisture to keep your home dry and cozy. This moisture is eliminated from the AC via a drain system that comprises two main components – a drainpipe and a drain pan.

Over time, and especially if maintenance isn’t good enough, water standing in the drainpipe can cause the growth of algae, which can potentially block the pipe. A blocked pipe often causes water to back up into the pipe and into the rest of the compressor, often resulting in a complete system shutdown.

Solution: Most HVAC experts recommend using vinegar to keep the drain line clear. With the AC shut, pour a small amount of vinegar down the line a few times each year to break up any build-up and flush it through the line.

7. Low Refrigerant Levels

Although coolant refrigerant doesn’t go bad or deplete, leaks can result in low refrigerant levels. Even a small leak can result in low refrigerant levels after several days. When you have low refrigerant, the air conditioner’s capacity to absorb heat from indoor air diminishes.

Causes of low refrigerant range from a leaking line set to flare issues. However, most of the time, the problem is a result of wear and tear. Over time, parts of the AC through which refrigerant cycles may wear, resulting in holes. Evaporator and condenser coils are two good examples.

Solution: Unfortunately, diagnosing leaking refrigerant can be a tall order. You need a dye test or nitrogen test to confirm that there’s a leak. For this reason, it’s best to engage an HVAC expert. Remember also that refrigerant is harmful to your health.

Key Takeaway

The mini-split can fail to blow cold air for many reasons, ranging from a blocked filer to a malfunctioned compressor. Therefore, it’s critical to ensure regular maintenance to avoid these issues. However, after the issue occurs, you can still take steps to personally rectify the problem – as long as you know when to call a professional technician.

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