When your air conditioning system won’t turn off, you might stress about the AC, the whole HVAC system in your house, your energy bill or if a system replacement is going to be a huge financial issue. What can cause an AC to never shut off?

When an AC is running and never or rarely cycles off as it should, the issue could be a variety of malfunctions or different parts. Frozen coils, filters, fans, switches, the thermostat or something else you’ve never thought about could be the problem. Some of these fixes are ok to do on your own. If your AC unit and HVAC system needs expert service, our technicians are ready to serve you and get you cool and comfortable again.

Should an AC Ever Run Nonstop?

Even in the middle of a hot and humid summer, an air conditioner should not be running nonstop, all day. No matter the heat outside, a unit should cycle on and off as designed. Cooling cycles should last about 15-20 minutes. A system should turn on and off on its own two or three times an hour. Once you set the thermostat the AC unit should reach the set temperature and turn off until another on cycle is needed, which will probably be in just a few minutes on a summer day.

If your AC is running for constantly for hours, it’s the sign of a problem you need to address. Nonstop running or not cycling will cause wear on the system, units and components. You’ll get a crazy energy bill. The fixes for a busted or failed system are more expensive than addressing the problem as soon as you recognize it.

Why is this Happening?

The Thermostat

It could be an issue with how a thermostat is programmed. Thermostats can break down though. They need replacement about once a decade. If you haven’t gone to a programmable or smart thermostat, then the overall functionality and efficiency of the heating and cooling might be less than what it should be. A thermostat’s sensors can become worn. Wiring from the thermostat can become worn or loose over a lot of years. It might not be telling the whole system what to do very well no matter the temperature or setting.

Thermostat Settings

On occasion, the reason the AC is on nonstop is the setting has been changed to “on.” The system will run continuously. It is set to “on” with the motor and fan running, but no air conditioning, or cooling, is operating.

Be it accidental, or hitting the wrong button on an app, or another person in the house messing with the thermostat, or a power outage resetting everything, anything could cause this and you might not think to check a simple issue. If you have a newer smart thermostat and need help setting it or using an app for it, contact a pro.

The Wrong Sized AC

Your AC or HVAC could be mismatched, too small or too large, for your home. When a cooling system is too little or undersized, it doesn’t have enough power to achieve the temperatures you set on the thermostat. The system eats a large amount of power, which is lost in ineffective, never-ending air conditioning. The unit runs for hours without keeping the interior at a comfortable temperature. This will deteriorate until the entire unit or system needs replacement.

Electrical Problems

Air conditioners have many electric parts and components. A stuck relay switch permits an electrical circuit to stay closed, supplying steady power to the AC unit. A compressor contactor can fuse in a shut position, so the condenser unit will go on running with constant power. Occasionally a stuck switch can be fixed DIY style, but generally you’ll need to have a technician find this and safely handle it.

A Stuck Switch

Even if you have the thermostat settings right, a stuck fan switch may make the fan motor run continuously while the AC is, overall, cycling correctly. A fan limit switch can become stuck. Resetting this switch near the blower fan should fix it.

Evaporator Coils

Evaporator coils can become dirty or frozen – yes even in July. To cool an indoor space, hot air goes through the system and passes over an evaporator coil. Refrigerant and evaporation combine to cool the air which then flows into the house.

Dust, dirt, pollen and so on can gather and build up on the coil. This makes it inefficient, and can lead all the way to a failure. The AC will keep running and running because it’s sensing “too warm” but the air from the coil isn’t cooling anything.

Evaporator coils can freeze. This will result in warm or hot air coming from your vents, even while set on cool, even on a summer day. Other issues in an HVAC system can stop heat from getting to the coils. The constant evaporating and condensing moisture freezes on the coils. Now refrigerant will not cool the air as designed. This problem can cause a bunch of other system malfunctions.

The Outdoor AC Unit

If the outdoor condenser unit is dirty, blocked with weeds, mulch or debris, the airflow of everything going in and out of the house may be inefficient. A condenser unit can be too dirty at the top, on or over the fan blades, or along its sides or base. Part of some spring yardwork and clean-up should be giving the AC unit space to operate.

Old Filters

We all know we should change the air filters in the house as recommended.  How often does this really get done? A dirty, clogged filter harms the airflow and clean air quality of a whole HVAC system. This is a simple step to help your cooling system in the short and long term.

Refrigerant Level

Air conditioners operate correctly with the right amount of refrigerant. If there are damaged components, leaks or it’s been many years since anyone checked the refrigerant, this could mean the AC is running but at far less than full efficiency.

At South End Heating and Air we specialize in HVAC and furnace repair, call us for a free consult and free estimate. We’ll evaluate your system and help make recommendations for optimum value. After all, we want to keep you cool all summer long and warm in the winter. Just schedule a visit with one of our technicians to talk about how we can help with your heating needs. Would you like to learn more options our techs can help you with? Give us a call 704-684-5339.