Why Your AC Runs Constantly and Never Shuts Off

Your neighbor’s AC clicks off after twenty minutes. Your AC runs constantly, and the house still feels sticky. Something is wrong, and it is not just the Idaho Falls heat.

Here is the short version. A healthy air conditioner should run in cycles, roughly ten to twenty minutes at a time, then rest. If yours never shuts off, five things usually explain it. A clogged filter, a refrigerant leak, a bad thermostat, an undersized system, or dirty coils. Each one forces your AC to work overtime without ever finishing the job.

Let’s walk through each cause the way our technicians actually diagnose it, starting with the cheapest fix first.

Check the Filter Before You Call Anyone

This is where many of our “my AC won’t stop running” service calls end up. A clogged filter chokes airflow. Your blower motor strains to push air through. Your evaporator coil gets colder than it should. The whole system slows down instead of speeding up. Homes near farmland or gravel roads around Ammon and Rigby clog filters fastest. Pull yours out and hold it up to a light. If you cannot see light through it, replace it. That single step resolves more nonstop-running calls than any other fix on this list.

Rule Out a Refrigerant Leak

Refrigerant does not get used up like gas in a car. If your levels are low, refrigerant is leaking somewhere in the line set or coil. That leak will not seal itself. A low charge means your AC pulls heat out of the air far more slowly than it should. The system senses the house is still warm and keeps running. It ends up chasing a temperature it cannot reach. You might also notice ice forming on the copper line near the outdoor unit, which is a dead giveaway. This one is not a DIY fix. Locating a leak, sealing it, and recharging the system correctly takes proper gauges and training.

Suspect the Thermostat Before the AC Itself

We get calls where the homeowner already replaced a capacitor or a filter. The AC still will not shut off. Half the time, the real problem was never the AC. It was a thermostat reading the wrong temperature. A thermostat on a sunny wall gets fooled into thinking the room is warmer than it is. So does one placed near a floor vent. Dead batteries cause the same confusion in battery-powered models. Before assuming the worst about your system, check the thermostat location and swap the batteries.

Consider Whether the Unit Was Ever Sized Correctly

Idaho Falls has a lot of homes that started small and grew. A finished basement here, a bonus room addition there, and suddenly a system sized for 1,800 square feet is trying to cool 2,600. An undersized AC cannot lose this fight no matter how well it is maintained. It will run nonstop on hot afternoons and still leave you a few degrees short of your thermostat setting. The only real fix is a Manual J load calculation to confirm what size unit your home actually needs, followed by a properly matched replacement if the current one falls short.

Look at the Coils, Not Just the Filter

Filters get all the attention, but coils quietly cause just as many problems. The outdoor condenser coil needs open airflow to release the heat your system pulls from inside your home. Grass clippings, cottonwood fluff, and dust build up fast during an Idaho summer and choke that airflow from the outside in. The indoor evaporator coil can develop its own layer of grime over years of use, especially if filters were skipped along the way. Either dirty coil forces the system to run longer to move the same amount of heat.

When to Stop Troubleshooting and Call a Pro

A little extra runtime during a 95-degree afternoon is normal and expected. What is not normal is an AC that runs around the clock, including overnight when temperatures drop into the 60s. That pattern means the system is failing to keep pace, not just working hard. The U.S. Department of Energy points out that neglected filters, coils, and refrigerant lines are the leading causes of declining AC performance over time. Left alone, a constantly running system tends to fail earlier and cost more to repair.

The Bottom Line

Start with the filter. Check the thermostat batteries and placement next. If your AC is still refusing to cycle off after that, the cause is mechanical and needs a trained eye. Our technicians run the same diagnostic order every time so we find the actual problem instead of guessing. Take a look at our AC service page for the full list of repairs, tune-ups, and replacements we handle across Southeast Idaho.

If your AC runs constantly, it’s not being efficient. It is asking for help. Contact our team or schedule service online, and we will track down the real cause. Curious what other Idaho Falls homeowners think of our work? Check our Google reviews or visit our homepage to see everything RSJ Mechanical offers.