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A malfunctioning air conditioning unit during the peak of summer, or worse – a heatwave – can be a homeowner’s worst nightmare. In fact, for many, a lack of conditioned indoor air is not only uncomfortable but can be dangerous for individuals at risk. If your outside AC unit isn’t turning on, it’s crucial to identify the cause quickly to restore comfort, safety, and prevent further damage.

Here are six common reasons your outside AC unit might not be working and when it’s time to call a professional.

1. Power Issues

One of the simplest and most common reasons for an AC unit not turning on is a lack of power. Check your circuit breaker to see if it has tripped. If it has, resetting it might solve the problem. If the breaker continues to trip, it’s a sign of a deeper electrical issue that requires professional attention.

2. Thermostat Problems

Your thermostat controls the AC unit. If it’s not functioning correctly, the AC won’t turn on. Ensure that your thermostat is set to “cool” and that the temperature setting is below the current room temperature. Replace the batteries if needed and make sure the thermostat is properly connected to the power source.

3. Clogged Air Filter

A clogged air filter can cause various issues, including preventing the AC unit from turning on. When the filter is dirty, it restricts airflow, causing the system to overheat and shut down as a protective measure. Check your air filter and replace it if it’s dirty. Regularly replacing air filters can prevent this problem and improve your system’s efficiency.

4. Refrigerant Levels

Low refrigerant levels can prevent your AC unit from working properly. If there’s a leak in the system, the refrigerant can escape, leading to insufficient cooling and potential damage to the compressor. Signs of low refrigerant include hissing sounds or ice buildup on the unit. Refrigerant issues require a professional technician who can locate and fix the leak and recharge the system safely.

5. Capacitor or Contactor Problems

The capacitor and contactor are critical components in the outdoor unit. The capacitor provides the initial jolt of energy to start the motor, while the contactor controls the flow of electricity. If either of these parts fails, the AC unit won’t turn on. Diagnosing and replacing these components should be handled by a professional.

6. Motor or Compressor Failure

The motor or compressor can fail due to age, lack of maintenance, or other mechanical issues. These are complex components, and their failure will usually prevent the entire system from operating. If you suspect a motor or compressor problem, it’s essential to call a professional technician.

When to Call a Professional

While some basic troubleshooting can be done by homeowners, many AC issues require the expertise of a professional. If you’ve checked the power supply, thermostat, and air filter and the unit still won’t turn on, it’s time to call Messmer Mechanical. We service and repair all makes and models of cooling systems so your home is cool comfortable in no time.