Why Isn't My Air Conditioner Cooling?
A homeowner's checklist for an AC or heat pump that runs but won't cool — the quick things to check yourself, and the signs it needs a technician.
Your AC is running but the house isn't getting cool — or it's blowing air that isn't cold. Some causes are quick DIY checks; others need a technician. Here's how to work through it.
Start with the quick checks
Thermostat set to "Cool" and below room temperature? Confirm the mode and that the setpoint is actually lower than the current temperature.
Fan set to "Auto," not "On"? With the fan on "On," it runs constantly — including when the system isn't actively cooling — so you feel room-temperature air and assume the AC failed.
Is the air filter clogged? This is the most common cause of weak cooling. A dirty filter chokes airflow, which can freeze the indoor coil and drop your cooling to almost nothing. Replace a dirty filter and give the system time to recover.
Is the outdoor unit running and clear? Walk outside — the outdoor unit's fan should be spinning. Clear any leaves, grass, or debris, and make sure there's about two feet of clearance around it for airflow.
Check for a frozen coil
If cooling has gotten steadily worse, look for ice on the refrigerant lines or the indoor coil. A frozen system usually comes from restricted airflow (that clogged filter again) or low refrigerant. If you see ice: turn the system to "Off" but leave the fan running to help it thaw, and check your filter. If it keeps freezing, that points to a professional issue.
Check the breaker and drain
- Tripped breaker: If the outdoor unit is completely dead, check your electrical panel for a tripped breaker.
- Full condensate drain: Many systems have a safety switch that shuts down cooling if the condensate drain backs up. A clogged drain line can stop the system entirely.
Signs it needs a technician
If the basics check out and you're still not cooling, the usual culprits need a pro:
- Low refrigerant / a refrigerant leak — a system low on refrigerant can't cool properly, and topping it off without fixing the leak is a temporary band-aid.
- A failing compressor — the heart of the outdoor unit.
- A bad capacitor or contactor — common electrical failures that stop the unit from starting.
- Ductwork problems letting cool air escape before it reaches your rooms.
A note on heat pumps
If you have a heat pump, it cools in summer by running in reverse — so the same checklist applies. If it heats but won't cool (or vice versa), the reversing valve or controls may be the issue, which is a technician job.
The bottom line
Filter, thermostat settings, and a clear outdoor unit solve a lot of "not cooling" calls for free. If you've checked those and you're still warm — especially during a heat wave — it's worth a service call before a small problem becomes a dead system on the hottest day of the year.
Still not cooling after the basics? Contact us or call (360) 825-0800. We offer same-day service when it's urgent — see emergency HVAC repair.
More resources
How Long Do HVAC Systems Last?
Typical lifespans for furnaces, heat pumps, AC, and ductless systems, what makes them last longer or die early, and the signs yours is near the end.
How Often Should You Service Your HVAC System?
A simple maintenance schedule for furnaces, heat pumps, and AC — what to do yourself, what a pro should handle, and what skipping it actually costs.
Repair or Replace? An Honest Framework
A real decision framework for the moment your HVAC system breaks — from a company that makes more money if you replace.
Ready to Talk?
Our team is here to answer your questions and help you find the right solution for your home.