Quick answer
Before calling for HVAC repair, check the thermostat mode and setting, replace a dirty air filter, look for a tripped breaker or a switched-off disconnect, and check whether the condensate drain switch has shut the system off. If a breaker trips twice, you smell gas or burning, or a carbon monoxide alarm sounds, stop and call a professional.
Plenty of no-cooling and no-heat calls turn out to have a simple cause a homeowner can check in a few minutes. This checklist covers the safe things to look at first, in the order we'd check them.
Never open electrical panels inside the equipment, handle refrigerant, or bypass a safety switch. If something on this list doesn't fix it, that's the point to call.
Stop First: Call Right Away If You Notice Any of These
- A carbon monoxide alarm is sounding: get everyone outside, call 911, and don't go back in until you're told it's safe.
- You smell gas (a rotten-egg odor): leave the home without flipping switches, then call 911 and Atmos Energy's emergency line from outside.
- A burning, electrical, or melting-plastic smell from the equipment or vents.
- A breaker that trips again after one reset.
- Water leaking through a ceiling under the attic unit.
- Loud banging, grinding, or screeching from the indoor or outdoor unit.
Checklist: AC Running but Not Cooling, or Not Turning On
- 1ThermostatMake sure it's set to Cool, the set temperature is below the room temperature, and the screen isn't blank. Replace the batteries if it uses them.
- 2Air filterA clogged filter chokes airflow and can freeze the coil. Replace it if you can't see light through it.
- 3BreakersCheck the breakers for the indoor unit and the outdoor unit. Reset a tripped breaker once. If it trips again, leave it off and call.
- 4Outdoor disconnectThe box on the wall near the outdoor unit has a pull-out block or switch. Make sure it's in the on position.
- 5Drain safety switchMany DFW attic systems have a float switch in the drain pan or drain line. If the pan is full of water, the switch shuts the AC off to prevent a ceiling leak, and the drain needs to be cleared.
- 6Outdoor unitClear grass, leaves, and anything stacked against the unit. It needs open space to release heat.
Checklist: Ice on the Lines or Indoor Coil
Ice on the copper line or the indoor coil usually means low airflow or a refrigerant problem. Turn the thermostat to Off and the fan to On so the ice melts, which can take a few hours. Don't chip at the ice. Replace the filter and make sure vents are open, then try cooling again. If it freezes a second time, the system likely needs a refrigerant leak check.
Checklist: Furnace or Heat Pump Not Heating
- 1ThermostatSet to Heat, with the set temperature a few degrees above the room temperature.
- 2Furnace powerFurnaces have a light-switch style power switch near the unit. Make sure it's on, and check the furnace breaker.
- 3Furnace doorThe front panel presses a safety switch. If the panel isn't seated, the furnace won't start.
- 4FilterA clogged filter can make a furnace overheat and shut itself off.
- 5One resetIf the furnace tried to light and stopped, turning the power switch off for a minute and back on lets it try again. If it fails again, call rather than repeating it.
- 6Heat pump frostIn cold weather a heat pump's outdoor unit can frost over and briefly run a defrost cycle, sometimes with steam. That's normal. A unit that stays frozen solid isn't.
Checklist: Thermostat Problems
- A blank screen often means dead batteries, a tripped breaker, or a drain switch that cut power to the system.
- If the system short cycles (turns on and off every few minutes), check the filter first, then call. Short cycling can also point to an oversized system or a failing part.
- Smart thermostats can lose Wi-Fi or update their schedule. Check that the schedule and any eco or away mode aren't overriding your setting.
When to Call
If the checklist didn't solve it, call Family First Comfort at (817) 935-8540. We're open 24/7, we diagnose the real cause before quoting, and you get one flat price before any repair begins.