When Your Home AC Stops Cooling
What you are looking at, the handful of checks that are safe to make yourself, and where the line is.
What you are noticing is a description, not a cause
Cooling problems can show up in several ways. The air coming out of the vents is not cold. The air is cold enough but there is very little of it. Or nothing starts at all when the thermostat calls for cooling.
Each of those can come from several different places in the system, and they can come from more than one at once. Telling them apart takes measurements at the equipment. So treat what you notice as something to report, not something to solve. Noting when it started, whether it came on gradually, and which rooms are affected gives whoever works on the system more to go on than a guess at the part.
Checks you can make without tools
These are ordinary things a homeowner can look at. None of them involve opening equipment.
Read the thermostat
Check the mode it is set to and the temperature it is set to. A thermostat left on heat, on fan only, or set above room temperature will not produce cooling. If the display is blank or unresponsive, say so when you call.
Look at the filter, if your instructions say how
If the equipment documentation for your system describes where the filter sits and how to reach it, look at the one it names and follow those instructions. If it does not, or if reaching it means taking a panel off, leave it and mention the filter on the call instead.
Notice what is blocking air
Walk the rooms that feel warm and look at the supply vents and return grilles. Closed registers, a rug over a floor vent, or furniture pushed against a return all restrict airflow. Outside, look for anything stacked against the outdoor unit or growth crowding it.
Leave these to a professional
- Opening electrical panels or the equipment cabinet.
- Anything involving refrigerant, refrigerant lines or gauges.
- Capacitors, contactors, control boards and wiring.
- Disabling, bypassing or taping over a safety switch, float switch or limit.
- Resetting a breaker again after it has already tripped again. A breaker that keeps tripping is reporting a problem, not asking to be reset.
Follow the manufacturer instructions for your own equipment. Where they and this page disagree, the manufacturer instructions win.
Stop using the system if you see this
Smoke, sparking, or a burning smell means stop. Turn the system off if you can do that safely, leave it off, and do not restart it to see whether it happens again. If there is fire, or you think there may be, or anyone feels unwell, treat it as an emergency and get emergency help rather than waiting for a repair appointment.
You can skip all of this
None of these checks are required before asking for help. If you would rather not go looking at thermostats and vents, or you are not confident about any of it, that is a reasonable place to stop. Call and describe what the air conditioning is doing in ordinary words.
Where to go next
Ask about a repair
Describe what the system is doing and ask about availability. There is no form on this site, and nothing is booked until you agree to it.
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