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Window AC Compressor Cycle On and Off: Why And How To Fix It?

Window AC Compressor Cycle On and Off: Why And How To Fix It?

Window air conditioners (AC) are a convenient way to cool small spaces, but they can experience issues such as the compressor repeatedly turning on and off. To understand the causes behind this problem, we conducted extensive research and uncovered the following information.

Causes of Window AC Compressor Cycling On and Off:

  1. Faulty thermostat
  2. Incorrect thermostat placement
  3. Temperature sensor problems
  4. Clogged air filter
  5. Refrigerant leaks
  6. Freezing evaporator coil
  7. Dirty condenser coil
  8. Electrical issues
  9. Adverse weather conditions
  10. Faulty compressor

In this article, we will explore each of these possible causes in detail. While the list may seem overwhelming, many of these issues can be easily resolved. Read on to find out more about why your window AC compressor may be cycling on and off.

Window AC Compressor Cycling On and Off Explained

All air conditioners, including window units, shut off when the set temperature is reached. They will remain off until the internal temperature sensor detects a change and triggers the system to turn back on. However, when the compressor starts turning on and off without reason and fails to cool the space effectively, it is known as short cycling.

Short cycling, characterized by the AC cycling on and off every few minutes, requires prompt attention. Below are some possible reasons for this behavior.

  1. Faulty Thermostat
    A malfunctioning thermostat can cause the AC compressor to cycle rapidly. The thermostat plays a crucial role in regulating the temperature, and when it misreads the temperature and sends the wrong signal, the AC system starts turning on and off repeatedly. Low battery power in the thermostat can also lead to this issue.
  2. Incorrect Thermostat Placement
    Placing the thermostat in undesirable locations can result in inaccurate temperature readings, leading to frequent on and off cycles. Examples of poor thermostat placement include near direct sunlight, close to air vents, or next to areas that generate significant heat, such as the kitchen. Moving the thermostat to a more central location can solve this problem.
  3. Temperature Sensor Issues
    The temperature sensor (thermistor) in a window AC measures the room temperature and determines whether to continue running or shut off the compressor based on the desired temperature. Malfunctioning temperature sensors can cause the unit to cycle on and off inaccurately. Testing the sensor using a multimeter and consulting the AC’s technical specifications is recommended.
  4. Clogged Air Filter
    A dirty and clogged air filter restricts airflow, leading to various problems, including short cycling. Additionally, clogged filters can increase power consumption and cause the AC compressor to cycle frequently. Regularly replacing or cleaning the air filter is essential to prevent larger issues. If short cycling persists, it’s advisable to have a technician examine other internal components.
  5. Refrigerant Leaks
    Refrigerant leaks can cause the AC system to run out of coolant, resulting in low refrigerant levels. Contrary to popular belief, low refrigerant levels are caused by leaks, not by the cooling process. Low pressure due to refrigerant leaks can lead to compressor malfunction and frequent shut-offs. Addressing refrigerant leaks should be done by a reliable HVAC service.
  6. Freezing Evaporator Coil
    Ventilation problems or refrigerant leaks can cause the evaporator coils to freeze up. When this occurs, the AC compressor, or occasionally just the outdoor unit, shuts off until the ice thaws and then turns back on. If the outside unit continues to have ice buildup after checking the air filters, it is likely due to a refrigerant leak, which requires professional attention.
  7. Dirty Condenser Coil
    If the outside AC unit repeatedly turns on and off and hasn’t received regular maintenance, the condenser coils may be covered in dirt and debris. If the condenser coils are blocked, the AC may overheat, causing the compressor to cycle on and off. Routine AC maintenance by a local HVAC company can help prevent this issue.
  8. Electrical Issues
    Electrical problems within your home’s electrical system can cause the AC compressor to cycle on and off. AC units consume a significant amount of electricity, and if the electrical load exceeds the capacity of the system, frequent on and off cycles can occur. Consulting an electrician is recommended if electrical issues are suspected.
  9. Adverse Weather Conditions
    Unusual or extreme weather conditions, such as extreme heat in the summer, can cause the AC unit to overheat and function improperly, leading to frequent cycling. Protecting the unit from adverse weather or waiting for conditions to normalize are potential solutions.
  10. Worn-Out Compressor
    A compressor nearing the end of its lifespan can cause the AC to cycle frequently. This scenario is the worst-case scenario as it may require replacing the compressor or the entire unit. Recognizing warning signs, such as reduced airflow, excessive noise, circuit breaker tripping, or increased power costs, can help prevent further damage. Seeking assistance from an AC repair professional is advised.

Cost Of Window AC Repair Or Replacement

Repairing a window AC can range from $50 for minor issues to $900 for more serious problems, with an average cost of $245. Comparing the repair estimate to the price of a replacement unit is recommended to determine the most cost-effective option. Window AC units can cost anywhere from under $150 to over $500 per unit.

Lifespan Of Window AC

A well-maintained window AC can last approximately 10 years. Regular cleaning and addressing maintenance issues can extend its lifespan. Consulting the usage and care manual specific to your unit is recommended to maximize longevity.


While some individuals may have the technical knowledge to address these issues independently, it is advisable to rely on professionals for technical matters. Their expertise ensures long-lasting solutions and prevents further recurrence of the problem.

Window AC Compressor Cycle On and Off: Why And How To Fix It?

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Written by HVAC Contributor

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