- A clogged air filter is the leading preventable cause of AC failure — it restricts airflow and can freeze the evaporator coil within hours.
- Tripped breakers and failed capacitors account for a large share of no-cool calls and are fast to diagnose and replace.
- Refrigerant charge loss is often slow and gradual — the system cools poorly for weeks before stopping completely.
AC runs continuously but the house stays warm
If the outdoor unit runs and the indoor air handler moves air but the space won't cool below 78–80 °F on a hot day, the system is under-performing rather than failed. Dirty condenser coils, low refrigerant charge, or a partially failed compressor are the primary causes.
Outdoor unit isn't running but indoor blower is
A failed capacitor or contactor prevents the outdoor compressor from starting while the indoor blower continues. The capacitor is a straightforward flat-rate replacement — and it's one of the most common summer failures across Mundelein and Des Plaines.
What homeowners can safely check first
Replace or inspect the air filter, verify the thermostat is set to COOL with the setpoint below room temperature, and check the outdoor unit's disconnect box. A breaker that has tripped partially — neither fully on nor off — may need to be cycled off and then on firmly.
Frozen evaporator coil — symptom and cause
A frozen coil blocks airflow completely and turns the air handler into an ice block. Common causes are restricted airflow (clogged filter) or low refrigerant. Shut the system off and let the coil thaw for 2–4 hours before restarting — running it frozen damages the compressor.
Failed capacitor causes immediate compressor shutdown
Capacitors provide the starting torque for compressor and fan motors. A failed capacitor often results in a humming outdoor unit that won't fully start. Running a compressor with a failed capacitor burns the compressor motor within minutes.
Refrigerant leak continues after recharge without leak repair
Adding refrigerant without finding and fixing the leak is a temporary measure — the system will return to low charge within weeks or months. Legendary performs leak detection before recommending a recharge.
Questions homeowners ask
- Should I keep running the AC if it's blowing warm air?
- If the air handler is moving air but not cooling, running it doesn't cause immediate harm. If the system is making unusual sounds or the outdoor unit is struggling to start, shut it off to prevent compressor damage and call for service.
- What is a capacitor and why does it fail in summer?
- A capacitor stores electrical charge to start compressor and fan motors. Heat accelerates capacitor degradation — that's why failures cluster on the hottest days. A capacitor replacement is a flat-rate repair that typically takes under 30 minutes.
- Does Legendary offer a Free Second Opinion on AC repair quotes?
- Yes — if another company has quoted a repair or replacement, Legendary will provide an independent flat-rate assessment at no charge.
Editorial provenance
Content by Legendary Service editorial team
Updated:
Methodology
Guidance compares the stated system factors, applicable utility program rules, and the conditions that must be confirmed in the home. Figures are planning ranges, not quotes; Legendary Service provides an upfront flat-rate price after diagnosis.