AC Not Cooling in DFW Heat: 6 Checks Before You Call an HVAC Company
October 6, 2026 · AC/DC Refrigeration & Appliance Repair
When a North Texas afternoon is sitting at 103°F, an air conditioner that is merely struggling feels identical to one that is broken. Some of the difference you can establish yourself in about ten minutes, without tools and without opening anything that bites. We are based in Grapevine and run these calls across Southlake, Colleyville and the north side every summer; here is the order we would check things in, and the two places where an owner should stop.
1. The thermostat — mode, setpoint, and batteries
Start here because it is free and because it is genuinely the answer more often than people expect. Confirm the mode is COOL and not FAN or AUTO-changeover, that the setpoint is at least a few degrees below the current room reading, and that a battery-powered stat has fresh batteries. A dying thermostat battery can hold the display alive while the relay that calls for cooling no longer closes, which looks exactly like a dead system from the hallway.
2. The filter
A loaded filter starves the indoor coil of air. Less air across the coil means the coil runs colder than it should, which is how a filter nobody changed in eight months turns into a block of ice on the evaporator. Pull it out and hold it up to a light. If you cannot see light through it, replace it — and if the system has been running that way for a while, expect the next check to matter.
3. Ice on the refrigerant line or the indoor coil
Go to the indoor unit and look at the larger of the two copper lines, the insulated one. Frost or a sleeve of ice on it means the evaporator is freezing. If you find ice, switch the system to OFF and set the fan to ON. The blower will move room air across the coil and thaw it — usually one to three hours. Do not chip at it and do not run the compressor while it is frozen.
Thawing it is not the repair. Ice is a symptom of restricted airflow or low refrigerant, and those two need to be told apart by measurement. If it freezes again after a fresh filter, the airflow explanation is used up.
4. The outdoor unit — power, clearance, and a coil you can see through
Walk outside while the system is calling for cooling. The fan on top should be spinning and the air coming off it should be warm. If the fan is still but you can hear a hum from the unit, shut the system off at the thermostat and leave it off — that is a motor or capacitor fault and running it that way cooks the compressor.
Then look at the coil around the outside of the cabinet. In this part of Texas it fills with cottonwood, grass clippings and the dust that follows every dry spell. If the fins are matted, the unit cannot reject heat, head pressure climbs and capacity falls away exactly when you need it. Keep two feet of clear air around the cabinet and keep the shrubs off it.
5. Breakers and the outdoor disconnect
An air conditioner usually has two breakers: the air handler and the outdoor unit. Check both at the panel. A breaker that has tripped once may simply have had a hot afternoon; a breaker that trips again within minutes is telling you something is drawing current it should not, and resetting it repeatedly is how a nuisance becomes a fire. Reset once. If it goes again, stop and book the call.
There is also a pull-out disconnect in a small box on the wall beside the outdoor unit. If someone has been working in the yard, it is worth confirming it is seated.
6. The condensate drain and the float switch
A cooling coil produces water, and that water leaves through a drain line that in most DFW homes runs to a pan or outside. Algae blocks it, the pan fills, and a float switch cuts the system off on purpose to stop the overflow reaching your ceiling. A system that shuts down on a hot day with no other symptom, and a pan with standing water in it, is the classic picture. Clearing the line is sometimes a shop-vac job at the outdoor end; a float switch that keeps tripping afterwards is not.
The two you should not touch
- Refrigerant. A sealed system does not consume refrigerant. If it is low, it leaked, and adding gas without finding the leak buys the identical repair again next season. It also requires certification to handle legally.
- Anything inside the outdoor electrical compartment. The run capacitor stores a charge after the power is off and is entirely capable of hurting you. Capacitors and contactors are cheap parts and a routine replacement for a technician — they are not a homeowner job.
What we actually do, and what we do not
This is a diagnostics and maintenance service, not a replacement business. We test and measure, we repair components — capacitors, contactors, motors, controls — we clean coils, and we tell you plainly when a system is genuinely at the end of its life. What we do not do is arrive with a quote for a new system already written, which matters because the company diagnosing the fault is very often the company selling the replacement. The full explanation lives on the HVAC diagnostics page.
What happens when you book
Have three things ready and the visit gets shorter: what the thermostat reads versus what you set it to, whether the outdoor fan is turning, and whether there is ice anywhere. The $90 diagnostic covers the visit and is waived when you proceed with the repair. We do not publish repair prices and we do not quote them by phone — you get a flat-rate quote in writing before any work starts. Same-day on calls before 2 PM, Monday to Friday 8 AM–4 PM and Saturday 8 AM–1 PM.
Where to go from here
The service page with the full diagnostic method is HVAC diagnostics in Dallas–Fort Worth. If check four was your problem, the coil cleaning guide covers what goes on a condenser coil and why the product is chosen by coil type. City pages for the north side: Grapevine, Southlake and Colleyville. To reach us, the contact page is here.
More from the blog: all guides and troubleshooting articles.