1. Thermostat — set to COOL, mode and temp correct?

Sounds obvious. About 1 in 12 service calls we run is a thermostat set to HEAT or FAN ONLY after someone bumped it. If you have a smart thermostat (Nest, Ecobee), check the schedule — vacation mode often gets left on.

2. Air filter — when did you last change it?

A clogged filter is the #1 reason coils freeze and cooling stops. Pull the filter out. If you can’t see light through it, replace it. Run the system for 30 minutes and check again — if it’s blowing cold, you’re done. If filter is fine, move on.

3. Breaker — flipped or reset?

Find the AC breaker in your panel (usually labeled AC or HVAC). If it’s in the middle position, flip it fully OFF and then back ON. If it trips again immediately or within minutes, stop — that’s an electrical issue and the unit needs a tech.

4. Condensate drain — clogged?

Many modern AC units have a float switch that shuts off cooling when the drain backs up — to prevent water damage. If your air handler is in the attic and you find water there, this is your problem. Clear the line by attaching a wet/dry vacuum to the outdoor termination point for 60 seconds. Pour a cup of distilled vinegar down the indoor cleanout afterward to keep algae from regrowing.

5. Vents — open and unblocked?

Walk every room. Closed vents create back-pressure that can stall the blower or freeze the coil. Furniture pushed against a return is just as bad as a closed supply. Open every register, clear every return.

6. Outdoor unit — fan running, coils clean?

Walk outside. The fan should be spinning whenever the system is calling for cooling. If it’s not — listen for a hum without movement (that’s a stuck capacitor, $200 fix) or silence (electrical, needs a tech). Either way, hose off the outdoor coils with a garden hose; lawn clippings and dust block heat exchange.

7. Refrigerant — frost on the lines?

Look at the larger of the two copper lines coming out of the outdoor unit. If it has frost or ice on it, you’re low on refrigerant or have a frozen indoor coil. Either way, shut the system off, switch thermostat to FAN ONLY for 2 hours to thaw it, then test cool again. If frost comes back within a day, you have a refrigerant leak — stop running the system and call us.

If none of these worked

You’re likely looking at one of: failed compressor, low refrigerant from a leak, blower motor failure, or contactor/capacitor failure. All of these need a tech with gauges and a meter. We diagnose with our $89 service call (waived if you approve the repair the same day) — call (561) 510-9414.

FAQ

Why does my AC freeze up only at night?
Lower outdoor temperatures + airflow restriction (clogged filter, closed vents, undersized return) = below-freezing coil temperature. Fix airflow first.

Can I add my own refrigerant?
No. EPA rules require a 608-certified tech to handle refrigerants. Cans sold at hardware stores are also a different (incompatible) refrigerant blend that will damage your system.

How long should I wait before calling?
After running through these 7 checks, if the system still won’t cool to setpoint within 2 hours and the indoor temp is rising — that’s the moment to call. In summer, indoor temps above 82°F start risking food spoilage and pet/elderly health.

Need it diagnosed today?

AtlantFlow runs same-day service across Palm Beach, Broward, and Miami-Dade. Licensed FL CAC1824422.

Call (561) 510-9414