Warm air from a running AC is the single most common call we get between June and September. Three of the nine causes you can fix yourself in ten minutes. The other six need a tech — here's how to tell which camp you're in.
Check these three first (free)
- Thermostat is set to COOL and the fan is on AUTO, not ON. Fan set to ON blows unconditioned air between cycles and feels warm.
- Air filter isn't clogged. A choked filter freezes the coil and kills cooling.
- The outdoor unit's breaker and disconnect are on, and the fan is actually spinning.
The six that need a technician
- Low refrigerant from a leak — topping off without finding the leak is throwing money away
- Failed run capacitor (the #1 part failure in Sacramento heat)
- Burned contactor so the compressor never engages
- Frozen evaporator coil from airflow restriction
- Failed compressor — the expensive one
- Dirty condenser coil packed with cottonwood, dust or pet hair
What to do while you wait
Turn the system off at the thermostat for a few hours if you suspect ice — running a frozen system can slug the compressor with liquid refrigerant and turn a $250 repair into a $4,000 one. Close blinds on the west side, run ceiling fans, and don't drop the thermostat below 72°; it won't cool faster, it just runs longer.
Frequently asked questions
Can I add refrigerant myself?+
No — it's illegal without EPA certification and overcharging destroys compressors. Low refrigerant also means a leak that needs to be found.
How much is a capacitor replacement?+
Typically $150–$350 installed in the Sacramento area, and it's usually a same-visit fix.
Why does my AC work at night but not in the afternoon?+
Classic sign of a marginal capacitor, low charge, or a dirty condenser — the system keeps up at 80° but not at 105°.
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