Why Is Your AC Running but Not Cooling? 7 Things I See All the Time
I get this call almost every week in the summer: “My AC is running, I can hear it, but the house just won’t cool down.” If you live in McKinney, Allen, Plano, Frisco or Celina, you know how hot a Texas afternoon can get when that happens.
The good news is that it isn’t always a big repair. Here are the seven most common causes I find on service calls, starting with the ones you can check yourself.
1. A dirty air filter
Honestly, this is the number one thing I find. A clogged filter chokes off airflow, and your system can’t cool what it can’t move. If it stays dirty long enough, it can even freeze up your indoor coil.
👉 Pull your filter and take a look. If it’s gray and dusty, swap it out. In Texas I recommend checking it every month during the summer.
2. Thermostat settings
It sounds too simple, but I’ve driven out to plenty of homes where this was the whole problem.
👉 Check three things:
- It’s set to COOL, not FAN or AUTO-FAN.
- The set temperature is lower than the current room temp.
- The batteries are fresh. A dead battery can make a thermostat act strange.
3. Blocked vents
A couch pushed over a return vent or a few closed registers can throw off the whole system. Your AC is designed to move a certain amount of air, and blocking it causes uneven cooling and extra strain.
👉 Walk the house and make sure the supply and return vents are open and clear.
4. A dirty outdoor unit
The outside unit is where the heat from your house gets dumped. If the coil is packed with dirt, grass clippings, cottonwood or leaves, the heat has nowhere to go.
👉 Keep about 2 feet clear around the unit. A gentle rinse from the outside with a garden hose is fine. Anything deeper, like cleaning the inside of the coil, should be left to a technician.
5. Low refrigerant (it’s a leak)
Here’s something a lot of homeowners don’t know: your AC doesn’t “use up” refrigerant like a car uses gas. If it’s low, there’s a leak somewhere. Just topping it off without finding that leak is a band-aid, and you’ll be calling again next summer.
Watch for these signs:
- Air from the vents that’s cool but not cold
- Ice on the copper lines
- A system that runs and runs and never reaches the set temp
👉 This one is for a licensed tech. Refrigerant work requires EPA certification and proper equipment.
6. A bad capacitor or other electrical part
The capacitor gives your compressor and outdoor fan the kick they need to start. In Texas heat, capacitors wear out a lot, and it’s one of the most common parts I replace. When one fails, you might hear humming outside while the fan doesn’t spin, or the unit tries to start and quits.
👉 Don’t open the panel yourself. Capacitors hold a charge even with the power off and can give you a serious shock. Call a pro.
7. A frozen evaporator coil
If you see ice on the indoor unit or on the lines, your coil has frozen. It’s usually caused by poor airflow (back to that filter!) or low refrigerant.
👉 Switch the thermostat to OFF and set the fan to ON to help it thaw, then give us a call. Don’t chip the ice off, because you can puncture the coil and turn a simple fix into an expensive one.
When it’s time to call a technician
If you’ve checked the filter, thermostat and vents and the air is still warm, it’s time to have someone take a look. Also call if you notice:
- Ice on the unit or the refrigerant lines
- Water leaking around the indoor unit
- Buzzing, grinding or clicking noises
- The system turning on and off every few minutes
- An outdoor unit that won’t start
- Cooling that’s gotten weaker over time
Catching a problem early almost always costs less than waiting until something fails completely, which usually happens on the hottest day of the year.
AC repair in McKinney, TX and surrounding areas
At Smartway Heating & Cooling, we handle AC repair, diagnostics, maintenance and new system installation for homeowners in McKinney, Allen, Plano, Frisco, Celina and across North Dallas.
If your AC is blowing warm air, can’t keep up, or won’t turn on at all, we’ll find the problem and give you straight answers about how to fix it.
AC not cooling? Call Smartway Heating & Cooling today, and let’s get your home comfortable again.
Need a hand with this? Call (469) 607-4241 or Book Service. We are open 7 days, 7am to 7pm.