Why Does My Unit Seem to Run All Day During the Summer?

First, the honest part: in a Houston summer, a healthy system is supposed to run a lot. When it's pushing 100 degrees outside and humid on top of that, your AC is fighting heat coming through the walls, windows, and roof all day long. On the hottest afternoons, a properly sized system may run nearly nonstop just to hold its set temperature — and that's normal. It's actually a sign the system is sized right: long, steady cycles are also how it pulls humidity out of the air.

So when should you worry? When the unit runs all day but the house still isn't comfortable, or when the behavior changed — it used to cycle on and off, and now it never stops. A few usual suspects:

• A dirty filter or coil. Air can't move, so the system works harder and longer for less cooling. This is the first thing to check, and the easiest fix.
• Low refrigerant from a leak. Less refrigerant means less cooling per minute of runtime, so the unit runs and runs without ever catching up.
• Leaky or crushed ducts, especially in a hot attic. You're paying to cool the attic instead of the rooms.
• A thermostat problem — wrong setting, bad location (in direct sun, for example), or a failing sensor.
• A unit that's undersized for the house, or a house that's gained heat load over the years — an addition, more sun after trees came down.

And one thing that isn't usually the fix: just putting in a bigger unit. An oversized unit cools fast and shuts off before it dehumidifies, leaving you cool but clammy — that's a whole topic of its own, and we'll get to it.

A couple of things you can check yourself: make sure the filter is clean, the thermostat is set to “cool” and “auto” (not “on,” which runs the fan nonstop), and that supply vents are open and unblocked. If all that looks right and the unit still runs all day without keeping up, that's when it's worth having a tech look at it — we'll test the system, find the real cause, and tell you straight what it needs.

Call or text (832) 605-5410 and we'll get it checked out.