Why AC Compressor Won’t Turn On: 8 Reasons & Easy Fixes

In this article, we’ll discuss 8 common reasons why AC compressor won’t turn on and how to fix them.

Why AC Compressor Won't Turn On
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Electrical Failures

Electrical issues are a primary suspect why AC compressor won’t turn on. Your unit requires a steady electrical current to function, and any disruption can cause it to cease operation.

Begin with checking your home’s electrical panel for any tripped circuit breakers or blown fuses. Circuit breakers are safety devices that trip when there’s an overload in the circuit. This is done to prevent electrical fires or damage to your devices. If you find a tripped breaker, you’ll have to reset it.

To reset it, switch it off and then back on. If it trips again, there may be a severe electrical issue. In such a case, consult an electrician. If a fuse is blown, replace it with a new one. Ensure that it matches the amperage required by your AC unit.

It’s safest to call a professional when dealing with electrical components and systems you are not familiar. Electrical problems can also include damaged wires or connections. These should only be inspected and repaired by qualified technicians. This is due to the risk of electrical shock or further damage to your system.

Thermostat Malfunctions

The thermostat is the control panel for your AC system. If it’s malfunctioning, your AC won’t receive the signal to start cooling. A common problem is a thermostat that is set incorrectly. Therefore, ensure it’s switched to ‘cool’ and that the temperature is set lower than the current room temperature. If your thermostat is battery-operated, a simple battery change might be needed. This is often the case if the display is not lit or if it’s behaving strangely.

With a non-responsive or irregularly behaving thermostat, the issue may extend to the internal wiring or the unit itself. Such instances do not require DIY fixes but professional attention. Advanced thermostats require precise calibration to function correctly. Incorrect settings or a misaligned sensor can lead to non-operation of the compressor.

It’s essential to follow the manufacturer’s instructions for resetting or recalibrating your thermostat. If you’re unsure, it’s better to consult a technician rather than risk further damage.

Refrigerant Issues

Refrigerant is the substance that your AC system uses to remove heat from the air in your home. If there’s a leak, the level of refrigerant will fall. As a result, the compressor may shut down to prevent damage from running on low refrigerant. When that happens, it can lead to overheating.

On the other hand, if the system has been overcharged with too much refrigerant, it can lead to increased pressure and temperatures. This may also cause the compressor to shut off. Both undercharging and overcharging can have severe repercussions for your AC system. Therefore, it’s crucial that a certified technician uses the proper tools to measure the refrigerant levels accurately.

Detecting a refrigerant leak involves searching for signs of oil residue around AC connections, as refrigerant carries oil that lubricates the compressor. Professionals use electronic leak detectors or UV dye tests to locate leaks reliably. After repairing any leaks, the technician will recharge the system to the manufacturer’s specifications.

Clogged Air Filters

Air filters play a vital role in maintaining the airflow through your AC system. When they become clogged with dust, pet hair, or other debris, they restrict airflow. This can cause the evaporator coils to freeze, leading to increased pressure and temperatures. This is one reason why AC compressor won’t turn on.

It’s recommended to check your air filters monthly and replace or clean them according to the manufacturer’s guidelines. Some filters are disposable and should be replaced with new ones. Others that are reusable and can be cleaned with water. Remember that in periods of high usage, such as the peak of summer, filters may need more frequent attention.

Damaged Compressor

The compressor is the heart of your AC system. It compresses refrigerant and pumps it throughout the unit. If it’s damaged, the entire system can fail to operate. Therefore, a damaged compressor is another reason why AC compressor won’t turn on.

Signs of a damaged compressor include strange noises like rattling or clicking when the AC is turned on. Another sign is that the compressor may not turn on at all.

Damage can occur due to several factors, including electrical failures, refrigerant issues, or simply wear and tear over time. Repairing a compressor is a complex job. Therefore, it should only be attempted by a professional with the appropriate expertise and tools.

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Defective Start Capacitor

The start capacitor provides the initial jolt of electricity to get your compressor moving. If it’s defective, the compressor might hum without starting. Alternatively, it may not make any noise at all if there’s no electrical current being provided.

Testing a capacitor involves using a multimeter like this AstroAI Multimeter Tester from Walmart. The multimeter is used to measure the capacitor’s capacitance and compare it with the rated capacitance listed on the component. This is a task for a professional, as capacitors can retain a charge even when the power is disconnected. Furthermore, they can be dangerous if handled improperly.

Incorrectly Sized AC Unit

An AC unit that is too small will struggle to cool your home. It will have to run constantly and this will potentially lead to overheating the compressor. The result is that the unit will shut down.

On the other hand, a unit that’s too large will cool the home too quickly. As a result, it will end up cycling on and off frequently. This can also lead to premature compressor failure.

Sizing an AC system requires a calculation called a Manual J load calculation. It takes into account your home’s size, layout, insulation levels, and other factors. This calculation should be performed by a qualified HVAC technician to ensure that the correct size unit is installed.

Poor Maintenance

Regular maintenance is critical for the longevity and efficiency of your AC system. This includes checking refrigerant levels, inspecting and cleaning coils, and replacing filters. Looking for signs of wear on electrical components is also part of this routine.

Neglect can lead to a build-up of dirt and debris. This can cause various parts of the AC, including the compressor, to work harder than necessary and eventually fail. An annual service by a certified technician will help to prevent unexpected breakdowns and extend the life of your system.

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