Why Does My Air Conditioner Turn Off By Itself? A Pittsburgh Tech Explains

Tired of your AC shutting off randomly?

We’ll help you troubleshoot this frustrating AC issue.

If your air conditioner is turning off by itself, your AC may have one of the following problems:

  • Thermostat is faulty
  • AC isn’t getting enough airflow
  • Condensate line is clogged
  • Refrigerant levels are low
  • AC is short cycling

Let’s look at each of these issues in more detail below.

Want a professional to repair your air conditioner? Our trusted technicians are standing by, ready to help!

Problem #1: Thermostat is faulty

You can think of the thermostat as the “brain” of your air conditioner. The thermostat sends signals to your AC system, telling it when to turn on and off.

Like all types of electrical equipment, thermostats can sometimes malfunction. The device itself could be causing errors or the wiring that connects the thermostat to the AC can develop a short, causing the system to shut off when it’s not supposed to.

You should contact a professional to inspect the thermostat and replace any faulty wires.

Problem #2: The AC isn’t getting enough airflow

To properly cool your home, your air conditioner needs to bring in a steady stream of warm air from your home. If your AC isn’t getting enough air, components like the blower will work harder to cool your home. Eventually, these components can overheat and shut down the AC.

One of the biggest restrictors of airflow is a dirty air filter. Since all air that enters your AC has to pass through the filter, if the filter is clogged with dirt, air can’t pass through.

Clean (left) vs dirty air filter (right)

Check your air filter to make sure it’s clean. If you see that the filter is covered in dirt, replace it with a new one.

Other causes of low airflow include:

  • Blocked vents: Make sure all the vents in your home are open and unobstructed so air can easily enter the return vents and exit the supply vents.
  • Fan problems: If your blower fan motor is malfunctioning, then your AC will have a hard time pulling in a sufficient amount of air. A professional will need to check the fan and possibly replace the fan motor if it’s broken.
  • Leaky ducts: You can have a professional inspect your ductwork to look for leaks or disconnected ducts.

Problem #3: The condensate line is clogged

Your air conditioner absorbs moisture from your home’s warm air. This moisture (called condensation) drains out of your home via a pipe so it doesn’t leak into your home.

Sometimes dirt and debris can enter the condensate pipe and create a clog. Instead of draining outside of your home, this condensation backs up into a drain pan. If the water reaches a certain level, it can trigger a switch that will shut off your AC.

Inside access point of the condensate line

You can try to clear the line yourself by going to the air handler (indoor unit) and locating the condensate line (usually a white PVC pipe). Remove the cap from the T-shaped part of the line and pour distilled vinegar into the line. Wait 30 minutes then flush the line with water.

If the clog persists or your AC keeps turning off by itself, contact an HVAC professional for further assistance.

Problem #4: Refrigerant levels are low

Refrigerant is the substance that cools your home’s air. If your AC is low on refrigerant (which means there’s a leak somewhere), then the resulting pressure change can trigger a safety switch that shuts down an important part called the compressor.

If your compressor shuts down, your AC will stop cooling your home’s air. The compressor will turn back on once the pressure has returned to safe levels.

That said, you’ll need to have a professional check for leaks and add refrigerant to your AC, or your AC will keep shutting off by itself.

You may have a refrigerant leak if you notice signs such as:

  • Hissing sounds coming from your AC
  • Water pooled around the indoor unit (frozen evaporator coil)
  • Loss of cooling power
  • Higher-than-normal energy bills

Problem #5: The AC is short cycling

Short cycling is when your AC turns off, then turns back on quickly. This “off/on” cycle continuously repeats, which causes significant wear and tear to your AC system and makes it difficult for your home to remain at a comfortable temperature.

Short cycling is caused by 1 of 2 problems:

  1. Your AC is too big for your home: An air conditioner that’s too big for your home will cool your home really fast, then shut itself off. Learn more about AC size and why it’s important by reading our blog, “What Size Central AC Unit Do I Need? A Pittsburgh Tech Answers.”
  2. The thermostat is installed in a bad location: If your thermostat is located near a window (where direct sunlight can hit it) or under an AC vent, then the thermostat can’t accurately detect the real temperature of the room. A professional will need to relocate the thermostat if this is the case.

If you recently installed your thermostat or AC system, short cycling may be what’s causing your system to shut off by itself. Contact the HVAC contractor who installed your system to make sure the air conditioner was sized correctly and that your thermostat is in the proper location.

Want a Pittsburgh professional to fix your AC?

Our trusted and certified technicians are happy to help. We give upfront prices before any repair work begins, which means there won’t be any surprises when you get the final bill.

Learn more about what to expect when you hire us by visiting our AC repair service page.