Why Your AC Is Not Cooling: 9 Real Causes We See on OKC Service Calls

Before you call anyone: 3 things to check yourself

About 1 in 8 of the no-cooling calls we get could have been solved by the homeowner in under five minutes. We still show up because we are not going to argue over a service fee, but we tell you what we found and we usually do not charge for it when the answer was a setting or a tripped breaker. Save yourself the call by checking these three things first.

• Thermostat mode. Is it set to COOL, not just ON? Is the fan set to AUTO, not always ON? An always-on fan keeps blowing air across the indoor coil even when no cooling is happening, which feels like warm air at the vents. Switch fan to AUTO.
• Indoor air filter. Pull it out and look at it. If you cannot see daylight through it, replace it. A blocked filter freezes the evaporator coil within hours and the AC stops cooling completely. We replace one frozen-coil filter at least twice a week in the OKC Metro during July.
• The disconnect box and the breaker. There is a small panel next to your outdoor unit (the disconnect) and a breaker in your main electrical panel labeled AC or HVAC. If the outdoor unit is silent, check both. Do not keep flipping the breaker if it trips a second time. That means something is wrong electrically and you need a tech.

9 actual causes ranked by how often we see them in OKC

These are the causes we see most on no-cooling calls across the OKC Metro from June through August. Ranked by frequency over the last three summers. Costs are 2026 OKC ranges, parts plus labor, before any maintenance plan discount.

1. Failed capacitor (the most common by a wide margin)

The capacitor is a small cylinder inside the outdoor unit that gives the compressor and the fan motor the jolt they need to start. When it dies, the outdoor unit either does not start, hums but does not spin, or starts and trips out within seconds. Capacitors fail because Oklahoma summers run them hard. A 2010-era 45 microfarad capacitor that should read 45 will often test at 22 to 30 by year 8 of service. Once it drops below about 32 microfarads, the compressor either will not start or works inefficiently until it does.

Fix cost: 150 to 300 dollars. Time on site: 25 to 45 minutes. Failure rate by July in OKC: about 1 in 11 systems over 8 years old.

2. Dirty outdoor condenser coil

The fins on the outside of your condenser unit have to dump heat into the surrounding air. Block those fins with cottonwood, grass clippings, dog hair, or general dust and the system cannot get rid of heat fast enough. Compressor runs longer, current draw goes up 20 to 35 percent, cooling drops off badly.

We see this most in Edmond neighborhoods with mature cottonwoods (Coffee Creek, Oak Tree, Spring Creek) and in older central OKC homes near trees. Cleaning cost: 150 to 300 dollars depending on how packed it is. If you do it yourself with a garden hose (power off first, gentle pressure), it is free.

3. Low refrigerant from a slow leak

Refrigerant does not get used up. If your system is low, you have a leak somewhere. Common leak points: the evaporator coil inside the air handler, the line set between indoor and outdoor units, the service valves at the outdoor unit, and the schrader valves used for service ports.

Symptoms: warmer than normal supply air, longer runtime, sometimes ice on the line set outside. The temptation is to just top off the refrigerant. We do not do that without finding the leak first. R-410A pricing in 2026 makes that math worse than it used to be (refrigerant alone runs 140 dollars per pound at the wholesale level, up from 80 in 2023). Leak diagnosis and repair: 400 to 1200 depending on where the leak is.

4. Frozen evaporator coil

If you pull the cover off your indoor air handler and the coil is covered in ice, the AC is going to blow warm air no matter what. The three most common causes of a frozen coil are a blocked air filter, low refrigerant, or a failed blower motor that is not pushing enough air across the coil. The system needs to be turned off and allowed to thaw fully (4 to 6 hours) before any diagnosis can happen.

Cost depends entirely on the root cause. Sometimes a 20 dollar filter. Sometimes a 1200 dollar coil replacement. We do not know until we see the cause.

5. Failed contactor

The contactor is the electrical switch that turns the outdoor unit on when the thermostat calls for cooling. Symptoms of a bad contactor: outdoor unit silent when it should be running, or chattering and clicking without actually starting. Usually fails in systems 8 to 15 years old after a lot of cycles in OKC summer load.

Fix cost: 175 to 325 dollars. Time on site: 30 minutes.

6. Bad blower motor or fan motor

If the indoor blower is not pushing air, the cool air never reaches your rooms. If the outdoor fan is not spinning, the heat does not leave the system. Both feel like the AC stopped working. Sometimes the motor itself failed. About 4 out of 5 times we look first at the capacitor that runs the motor, because a 22 dollar capacitor is a much cheaper fix than a 600 dollar motor and a worn capacitor often kills a motor that still had years of life.

Motor replacement cost: 400 to 900 dollars depending on size and brand.

7. Tripped breaker (do not keep resetting it)

If the breaker for your AC keeps tripping after you reset it, stop resetting. The breaker is doing its job. Something is drawing too much current and the cause needs to be diagnosed by a tech with a meter. Repeated resetting can damage the compressor or start an electrical fire.

Common underlying causes: a compressor at the start of failure, a failed capacitor under load, a short in the wiring, or a refrigerant overcharge from a prior service. Diagnostic cost: 100 to 200 dollars plus whatever the underlying repair runs.

8. Wrong thermostat programming or wiring

About 1 in 14 no-cooling calls turn out to be thermostat related. Either someone changed batteries and the programming reset, or wiring got bumped during a recent install, or the thermostat is mounted in a sun-hit hallway and is reading a falsely high room temp.

Fix cost: usually 150 to 400 dollars including diagnostics. Sometimes free if it is just a setting we walk you through over the phone.

9. Refrigerant overcharge from a prior service

This one we see specifically on systems that were serviced by another company in the last 18 months. A tech topped off refrigerant without measuring, the system is now over-charged, and the compressor cannot move heat efficiently. Symptoms look almost identical to a system that is low on charge.

Fix cost: 200 to 400 to recover the excess refrigerant and verify the correct charge. The bigger problem is that whoever overcharged it did not measure properly, which often means other things are misconfigured too.

What we do when we arrive

We check refrigerant pressures with gauges, capacitor microfarads with a meter (not by appearance), amp draw on the compressor and the blower, static pressure across the air handler if the issue might be airflow, and the condition of the outdoor coil. The visit usually runs 45 to 75 minutes for diagnosis. We tell you what we found with the numbers attached.

If the answer is a 22 dollar capacitor, we say so and we do not invent reasons to upsell you on replacement. If the answer is bigger (failed compressor, big refrigerant leak, evaporator coil), we walk you through the real cost and whether repair makes sense versus planning for replacement.

Related on this site

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• AC installation when replacement is the right answer
• why your summer energy bill doubles