By Hood Service Company · Corsicana, TX · Updated
The short version
- Check thermostat settings, the filter and the breakers before anything else.
- Whether the outdoor unit runs tells you a lot about where the problem is.
- Ice, buzzing or a breaker that keeps tripping are signs to stop and call for repair.
- On the hottest afternoons, a working system may run nonstop and still trail the setting by a few degrees.
What should you check first when the AC isn't cooling?
Confirm the thermostat is set to Cool with a setting below room temperature, the fan is on Auto, and the batteries are fresh. Then check the filter and the breakers for the indoor and outdoor units.
Our HVAC troubleshooter walks through the same checks one symptom at a time.
- Thermostat: set to Cool, a few degrees below the current reading. Replace the batteries if the display is blank or dim.
- Filter: a clogged air filter chokes airflow. If you can't see light through it, replace it.
- Breakers: look for a tripped breaker for the furnace or air handler and one for the outdoor unit. Reset it once. If it trips again, leave it off and call.
- Vents and returns: make sure supply registers are open and return grilles aren't blocked by furniture or rugs.
- Outdoor unit: clear leaves, grass clippings and anything stored against it.
What does it mean if the outdoor unit isn't running?
If the indoor fan blows but the outdoor unit is silent, a start-up part or control is the likely cause. If the unit hums without the fan spinning, turn cooling off, because the motor may be straining.
Once you've ruled out the breaker, the usual suspects are a failed capacitor, the part that gives the motors a starting boost, a worn contactor, or a control problem. A capacitor can hold a charge even with the power off, so this is strictly work for a technician.
Why is air coming out but not cold?
Air that moves but is only slightly cool usually points to a low refrigerant charge from a leak, a dirty outdoor coil, or an indoor coil that's starting to ice over.
Look at the larger insulated line where it enters the outdoor unit. A little sweat is normal; frost or ice means you should turn cooling off and read our guide to a frozen evaporator coil.
Refrigerant doesn't get used up. If the refrigerant charge is low, there's a leak, and the right fix is to find and repair it, not just add more.
Why is only part of the house cool?
Uneven cooling is usually an airflow problem: closed or blocked vents, leaky or crushed ducts, or a system that's too small for the rooms it serves. Rooms under the roof often run warmest in Texas heat.
Open every register and keep interior doors open while you test. If a room still lags, the ducts are the next suspect. Our guide to weak airflow and ductwork problems explains what a technician looks for.
Is it normal for the AC to run all afternoon in summer?
On the hottest North-Central Texas afternoons, it can be. A properly sized system may run almost continuously, fall a few degrees behind, and then catch up in the evening.
Systems are sized for the area's typical summer design conditions, not the most extreme hour of the year. What isn't normal is a house that keeps losing ground overnight, or a system that never shuts off on a mild day. Those point to low charge, a dirty coil or an airflow problem.
When should you stop and schedule a repair?
Stop once the safe checks are done. Anything involving refrigerant, capacitors, motors or a breaker that keeps tripping needs a trained HVAC technician, and running a struggling system can turn a small repair into a bigger one.
Book AC repair service and tell the technician what you already checked, which speeds up diagnosis. Hood Comfort Club members get priority service; see our maintenance plans for details.
When should you call a technician?
- The breaker trips again after one reset.
- The outdoor unit hums, buzzes or clicks but won't start.
- Ice forms on the refrigerant lines or the indoor unit.
- You notice a burning smell, or grinding, screeching or banging noises.
- Water leaks indoors around the furnace or air handler.
Frequently asked questions
Should I set the thermostat very low to cool the house faster?
No. A very low setting doesn't make a central air conditioner cool the house faster; it only makes it run longer and can contribute to coil icing. Choose the temperature you actually want and let the system work.
Can I add refrigerant myself?
No. Refrigerant work belongs with a trained HVAC technician who has the right equipment. A low charge also means there's a leak, and adding refrigerant without repairing it is only a temporary fix that can strain the compressor.
Why does my AC smell musty when it starts?
A musty smell often comes from moisture on the indoor coil, in the drain pan or in the ducts. Replace the filter and look to see that the condensate line is draining. If the smell continues, have the coil and drain inspected.
Is it a problem if my AC turns on and off every few minutes?
Frequent short cycles can mean an oversized system, a thermostat in a poor location, a dirty filter or a refrigerant issue. Short cycling wears parts faster and removes less humidity. If it keeps happening, schedule a check.