Why Does My AC Stop Working at Night?

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Updated September 16, 2022

Even if you have a top-tier AC unit, you may eventually encounter a frozen air conditioner at night. This air conditioning issue can be stressful as your home struggles to reach a comfortable temperature at night, especially during the summer heat. Unfortunately, air conditioning repair hacks won’t work without studying the potential causes of the problem. So, keep reading to learn, “Why does my AC stop working at night?”

KEY TAKEAWAYS:

  • If the temperature drops quickly at nighttime, the pressure change can negatively affect your AC system.
  • Low refrigerant and poor airflow can cause the evaporator coils to freeze, leading to diminished cooling power.
  • If your AC contactor breaks, your unit cannot turn off or on without changing a circuit breaker switch.

You may have a frozen evaporator coil whenever your central or window air conditioning unit stops working. In addition, if your AC isn’t cooling or the AC system runs nonstop, it could be insufficient airflow from dirty AC filters. In either case, it’s good to know what’s happening before you call an air conditioning service.

Insider Tip

You need a licensed HVAC professional to diagnose and treat a Freon leak because unlicensed people cannot legally handle air conditioning refrigerants.

Why an Air Conditioner Freezes at Night

Losing air conditioning efficiency at nighttime is a common problem for AC users, indicating a fault somewhere in the system. In addition to increased electricity consumption, your AC system may cause damage to your home from water or refrigerant leaks. Luckily, proper maintenance and preventative inspections can help mitigate severe problems.

Poor Air Flow

Dirty air filters, clogged vents, and damaged AC ducts can negatively impact the airflow in your air conditioner. Unless you clean your ventilation system regularly, the dirt and dust can prevent your AC from cooling your home.

Low Refrigerant

If your AC freezes and stops working, the issue could be a refrigerant leak. Low refrigerant levels cause the evaporator coils to get too cold, leading to frozen coils and diminished cooling power.

Outside Air Temperature

As the temperature drops at night, the pressure in the AC system will drop. If the outside temperature drops too quickly, your air conditioner may lose its cooling ability.

Defective Blower Motor

If your blower motor isn’t working, your air conditioner cannot pull air from your home to complete the heat exchange process. Fortunately, a broken blower motor is easy to spot. If the outdoor unit is running, but the indoor unit isn’t, the blower motor is faulty.

Warning

A dirty air filter in an AC unit will lead to insufficient airflow, warm indoor temperatures, and higher energy bills.

Bad Contactor

An AC contactor passes electricity from your home to the air conditioner’s components. The contactor can get stuck, leading to an AC unit that won’t shut down or turn on.

STAT: According to a 2020 US EIA (Energy Information Agency) survey, 42% of Americans have a programmable thermostat temperature. (source)

Why Does My AC Stop Working at Night FAQs

How do I defrost my AC unit?

Immediately turn off the system and change your blower fan setting to "on" if your system is frozen. The ice will thaw as the fans blow hot air over the frozen pipes. You can also pour hot water on the coils to quicken the defrosting process. Once the ice is gone, restart your AC system.

Why does my AC randomly stop?

Either your system is overheating, or the compressor is wearing out. Some AC systems have a safety auto-off feature that protects your air conditioner from additional damage. Basic troubleshooting for this issue involves checking your air filters and ensuring that the evaporator or condenser coil isn't frozen.

Why is my AC blowing out hot air?

If your system blows hot air, you may have an airflow issue. Dirty filters, blocked vents, and a faulty air conditioning blower are possible reasons for poor-quality airflow.
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