Mount Pleasant Heating & Air Conditioning · AC Troubleshooting
AC Running Non-Stop? Why & What to Check
An air conditioner that runs constantly — or never shuts off — is working too hard. Sometimes it is simply an extremely hot day; other times it is a sign of an airflow, refrigerant, or sizing problem. Here is how to tell the difference.
Quick Answer
An AC that runs non-stop usually means it cannot reach the thermostat setpoint: check the setpoint and filter first, then look for ice on the coil. Persistent non-stop running is often caused by low refrigerant, a dirty coil or filter, an undersized system, or a stuck contactor — a technician can measure the system and find the real cause.
Common Causes
What Usually Causes This Problem
Most of these problems come from a handful of causes. Each one links to the service that fixes it.
Thermostat Set Very Low
A setpoint far below the outdoor temperature means the system works far harder — and longer — to get there.
Dirty Filter or Coil
Restricted airflow makes the system run longer to move the same amount of heat. This is the most common fixable cause.
Low Refrigerant
A system low on refrigerant cools inefficiently, so it runs and runs without satisfying the thermostat.
Undersized System
An AC too small for the home or the heat load runs continuously on hot days and still struggles to keep up.
High Heat Gain
Poor attic insulation, unshaded windows, or heat-generating appliances add load the system must overcome.
Stuck Contactor
A contactor that welds closed keeps the compressor running even when the thermostat is satisfied.
Try These First
What You Can Check Yourself
Safe, free checks you can do in a few minutes before deciding whether to call.
Check the Setpoint
A reasonable setpoint is 70–74°F. Running the AC at 68°F or below on a 95°F day will make it run non-stop.
Replace the Air Filter
The easiest fix for a struggling system. A clean filter restores airflow and cooling efficiency.
Look for Ice
Ice on the indoor coil or outdoor line set means airflow or refrigerant trouble — thaw the system and call a technician.
Check the Outdoor Unit
Make sure the condenser fan is spinning and the coil is clean. A fan that barely turns reduces heat rejection dramatically.
Test One Room
If one room stays hot while others cool, it is usually an airflow or ductwork issue rather than the whole system.
Have the System Measured
A technician can check refrigerant charge, airflow, and sizing to find why the system never satisfies the thermostat.
Get It Fixed
Get It Fixed by a Pro
If the checks above did not solve it, stop guessing. A licensed technician will diagnose the real cause, explain your options, and give you the price before any work begins.
Common Questions
Straight Answers
Quick, honest answers to the questions we hear most from Mount Pleasant homeowners.
Is it normal for my AC to run all day in summer?
On very hot days a correctly sized system can run for long stretches — that is normal. The red flag is when it runs non-stop around the clock, never shuts off, or runs constantly even in mild weather. That indicates a real problem.
Why does my AC run non-stop but never cool the house?
The system is running but not removing heat effectively — usually low refrigerant, a dirty coil or filter, a failing compressor, or an undersized system. It needs professional measurement to diagnose.
Will a bigger AC solve the problem of it running all the time?
Not necessarily. An oversized system can actually cause short cycling and poor dehumidification. Correct sizing comes from a professional load calculation, not guesswork.
Does a continuously running AC use a lot more electricity?
Yes. Non-stop running is both uncomfortable and expensive. Fixing the underlying cause — whether a $20 filter or a refrigerant repair — usually pays for itself quickly in the Mount Pleasant summer.
Ready to Get Comfortable Again?
Call (843) 714-0863 or request service online. We are available 24/7 for emergencies and offer same-day appointments when available.
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