AC Blowing Warm Air in Chicago? Here's What's Wrong

Common causes of ac blowing warm air

1. Low refrigerant from a leak

If refrigerant is low, the system can't absorb heat from your home's air. You'll often see ice on the copper lines outside or hear hissing near the indoor coil. Refrigerant doesn't get 'used up' — if it's low, there's a leak. The leak must be found and sealed before recharging, or the new refrigerant will leak right back out.

2. Frozen evaporator coil

A dirty filter, blocked vents, or low refrigerant can cause the indoor coil to freeze solid. Once frozen, the system can't transfer heat — so air blows warm. Fix: turn the AC OFF, switch the fan to ON to thaw the coil (until fully melted), replace the filter, and call us if it freezes again.

3. Failed run capacitor

The capacitor is a small cylinder that gives the compressor and fan motors the kick they need to start. If it fails, the outdoor fan may spin but the compressor doesn't engage — meaning no cooling happens.

4. Thermostat misconfiguration

Sometimes it's the simplest fix: thermostat set to 'fan only' instead of 'cool', heat mode left on by mistake, or dead batteries. Check the thermostat is set to 'Cool' and 5° below room temperature first.

5. Outdoor unit not running

Walk outside and check — is the outdoor unit running? If not, it could be a tripped breaker, blown fuse, or failed contactor. The indoor blower can still push air (warm), but without the outdoor unit, there's no cooling.

Try these checks first (60 seconds)

1. Set thermostat to 'Cool' and 5° below room temp
2. Check the air filter — replace if gray/clogged
3. Walk outside and confirm the outdoor unit is running
4. Check for ice on the refrigerant lines or indoor coil
5. Check the breaker for the AC — flip OFF then ON

When to call SAVA

If none of those checks bring back cool air within 30 minutes — or if you find ice on the lines, hear hissing, or smell burning — call us right away. Running an AC that's not cooling puts extra stress on the compressor.

SAVA is a family-owned, EPA Section 608 Certified HVAC company serving Chicago and North Shore suburbs. We diagnose the exact fault before any work begins, carry common parts for same-day repairs, and give honest repair-versus-replace guidance. Learn more about our AC repair service or emergency AC repair.

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