A common question we hear often is “Why does my fan kick on but the compressor is not working?”. If this happens to you, do not jump to conclusions and assume that your entire HVAC unit is toast. This is an issue but things could be worse. To understand this issue, it is important to know what the compressor does. The compressor is the part of the exterior air conditioning unit that circulates refrigerant through the indoor and outdoor coils to cool your home or business. Bottom line is that if the compressor is not working, the unit cannot cool your house. It makes sense why this is such a common question and puzzling to diagnose as a home or business owner. The fan is located at the top of the exterior air conditioning unit and returns the warm air in your home or business to the condenser to later be converted to cool air that is dispersed into the interior of your home or business. Typically, if the fan is moving and working, the compressor is working as well.
There are a few things that could be happening to cause your compressor not work even though the fan has kicked on, such as:
- There is an electrical issue in the heating and air conditioning unit. In a split system, the indoor unit and outdoor unit receive power from two different sources. You could check the wiring between the two systems if you have experience with this and also reset the circuit breaker, but we HIGHLY recommend letting professionals deal with any sort of electrical issues.
- The coils or filters are dirty. Since there are so many moving parts of an air conditioning system, it is important for the units to have certain safety features to ensure they are running correctly. One of these features is that if the coils or filters become too gunked up with dirt and debris, the compressor will not be able to run and could turn off. Keeping these cleaning routinely will prevent this from being an option!
- There could be an issue with the AC capacitor. The AC capacitor powers the compressor, so if this goes out, the compressor will not turn on.
Additional Causes of a Non-Working Compressor When the Fan Kicks On
If your AC fan is running but the compressor isn’t working, it can be frustrating, especially in the heat of summer. While the problem may not mean your entire unit is doomed, diagnosing and repairing the issue requires an understanding of how the components function together. Beyond electrical issues, dirty coils, and a faulty capacitor, several other potential causes could explain why your compressor isn’t turning on. Let’s explore a few more reasons and discuss what to do if you encounter this problem.
1. Low Refrigerant Levels
One of the more common reasons a compressor won’t engage is low refrigerant levels. The refrigerant plays a crucial role in cooling the air, but if the levels are too low due to a leak, the system will lose efficiency. Modern AC units often have built-in safety mechanisms to prevent damage to the compressor if refrigerant levels drop too low. This can trigger the compressor to stop running even though the fan continues to operate.
To fix this issue, a certified HVAC technician will need to locate the leak, repair it, and recharge the system with refrigerant. Running an AC unit with low refrigerant not only prevents proper cooling but can also damage the compressor over time, leading to more costly repairs.
2. Faulty Contactor
The contactor is a small electrical component within your outdoor AC unit that controls the flow of electricity to various parts of the system, including the compressor. If the contactor is faulty or worn out, it might not send the necessary voltage to the compressor, even though the fan receives enough power to run. This can create a scenario where the fan kicks on, but the compressor remains idle.
Replacing a defective contactor is a common repair for HVAC technicians and is relatively inexpensive compared to other major components. However, as with any electrical issue, it’s best to leave this to professionals rather than attempting a DIY fix.
3. Thermostat Issues
The thermostat is the central control system of your air conditioner, sending signals to your indoor and outdoor units to either turn on or off based on the temperature setting. If the thermostat is malfunctioning, it could cause the fan to kick on without sending the appropriate signal to the compressor. The compressor and fan are designed to work together, so if the thermostat isn’t functioning correctly, it can disrupt this harmony.
Testing the thermostat and replacing it if necessary is one solution to ensure the correct communication between your system’s components. A thermostat that isn’t calibrated properly or is malfunctioning can be one of the simpler fixes.
4. Overheating or High-Pressure Switch
Another less obvious cause of compressor failure while the fan runs is overheating. Compressors generate a lot of heat when in use, and if they become too hot, they can trip a safety switch that shuts down the compressor to prevent damage. High-pressure switches can also shut off the compressor if the system pressure exceeds safe levels, often due to a refrigerant imbalance or blocked air vents.
In either case, the fan might continue running to help dissipate heat, but the compressor remains off until the system cools down or the pressure normalizes. If overheating is the issue, it’s essential to address the underlying cause, whether that’s insufficient airflow, dirty components, or a refrigerant problem.
5. Compressor Motor Failure
Like any mechanical part, the compressor motor can eventually wear out, particularly in older units. If the motor has failed, the compressor won’t function, even if the fan does. A compressor motor failure is often one of the more serious and costly repairs, potentially requiring a full compressor replacement.
In some cases, it might be more cost-effective to replace the entire air conditioning unit, especially if the system is nearing the end of its lifespan (10-15 years). A professional HVAC technician can help you assess whether a motor repair or replacement is worth the investment compared to a new system installation.
6. Blocked or Faulty Expansion Valve
The expansion valve regulates the flow of refrigerant into the evaporator coils. If this valve is blocked or malfunctioning, it can prevent the refrigerant from moving through the system, which in turn can cause the compressor to shut off. The fan may continue to run because the thermostat and electrical components are still operational, but without the refrigerant flowing properly, the compressor won’t engage.
Replacing or cleaning the expansion valve is a job for a qualified technician, as it requires disassembling parts of the AC system and rebalancing the refrigerant.
7. Incompatible Replacement Parts
If your air conditioning unit has been repaired before and the wrong replacement parts were used—such as an incompatible capacitor or compressor—it could cause issues with your system’s functionality. Mismatched parts can lead to a situation where the fan runs but the compressor doesn’t receive the right amount of power or signals to operate.
Always ensure that any repairs to your HVAC system use manufacturer-approved or compatible parts, as using generic or incompatible components can lead to more problems down the line.
Conclusion: Addressing a Non-Working Compressor
When the fan kicks on but the compressor doesn’t work, there are a number of potential causes ranging from minor electrical issues to more significant mechanical failures. By understanding the various components involved in your air conditioning system, you can better recognize the possible culprits behind compressor failure.
While some of these issues might be relatively simple fixes, others, such as refrigerant leaks or compressor motor failure, can require more complex repairs. Regular maintenance, including cleaning coils and filters and checking refrigerant levels, can help prevent many of these problems from occurring in the first place. If you’re unsure of the cause or uncomfortable with diagnosing the issue yourself, it’s always best to call a professional HVAC technician to ensure the job is done safely and effectively.
Call Coastal Home Services for help with your AC System
Are you having problems with your air conditioning system and not sure where to turn or who to call? There are so many intricate parts of a heating and air conditioning system, it’s no surprise that things will break eventually and need to be replaced. At Coastal Home Services we know how frustrating it can be for your air conditioning unit to randomly cut off, and self-diagnosing the issue can be extremely difficult and cumbersome. We would love to help you with your heating and air conditioning needs, whether that be coming out to fix a repair or providing routine maintenance on your unit. Whatever your HVAC needs are, our NATE certified team is here to help.
If your heating and air conditioning unit is more than ten years old and reaching the end of its life, the compressor not working when the fan kicks on could be an indicator to think about replacing your unit. If you are experiencing issues with your heating and air conditioning system, let our Trane® certified professionals at Coastal Home Services help you! Our company is the #1 provider for air conditioning and heating services on the Crystal Coast, so you can be confident that you are in the best hands. Whether it’s fixing an issue or providing routine maintenance on your unit, Coast Home Services is the company you can trust. Give us a call to schedule your appointment today or schedule a service using our online form.
