AC Not Turning On
Your AC system won't start at all — no fan, no cooling, no response.
AC Not Turning On: An AC that won't turn on is usually caused by a tripped breaker, a blown fuse, thermostat problems, or a failed capacitor. Check your breaker panel and thermostat first. If neither fixes the issue, you need a licensed HVAC technician. Repairs typically cost $125–$500.
What Causes This?
Tripped Circuit Breaker
The most common reason an AC won't start. The outdoor unit and indoor air handler have separate breakers. Check both in your electrical panel and reset if tripped.
Failed Capacitor
The capacitor provides the initial electrical jolt to start the compressor and fan motors. A failed capacitor makes a clicking sound but the unit doesn't start. Common in Sacramento's extreme heat.
Thermostat Malfunction
Dead batteries, incorrect settings, or a failed thermostat can prevent the system from receiving the signal to start. Try replacing batteries and setting to COOL/AUTO.
Blown Fuse in Disconnect Box
The outdoor disconnect box near the condenser contains fuses that can blow from power surges. This is separate from your main breaker panel.
Contactor Failure
The contactor is an electrical relay that sends power to the compressor. When it fails, the outdoor unit gets no power. A common wear item on older systems.
Safety Switch Triggered
Modern systems have safety switches (float switch for condensate drain, high-pressure switch) that shut the system down to prevent damage. A clogged drain line is a frequent trigger.
Can It Wait?
During Northern California summers, a complete AC failure is an emergency. Interior temperatures can exceed 100°F within hours. This is especially dangerous for elderly residents, young children, and pets.
What Does It Cost?
| Item | Cost Range |
|---|---|
| Breaker Reset | Free |
| Thermostat Replacement | $150–$500 |
| Capacitor Replacement | $150–$300 |
| Contactor Replacement | $150–$350 |
| Fuse Replacement | $75–$150 |
| Condensate Drain Clearing | $100–$250 |
Repair vs. Replace
Repair
Repair if: the issue is electrical (breaker, capacitor, contactor) and the system is under 12 years old.
Replace
Replace if: the system is 15+ years old, needs multiple repairs, or uses obsolete R-22 refrigerant.
Rule of thumb: Electrical component failures are usually inexpensive to fix. But if your system is old and fails frequently, invest the repair money toward a new system with SMUD rebates.
When to Call a Contractor
- ✓Resetting the breaker doesn't fix the problem or it trips again
- ✓You smell burning or see scorch marks near the unit
- ✓The system makes humming or clicking sounds but won't start
- ✓It's above 95°F and you have no backup cooling
- ✓You've checked the thermostat and filter with no improvement
Related Problems
AC Not Turning On — FAQ
Why won't my AC turn on at all?
Start with the basics: check your thermostat is set to COOL with the temperature below room temp, check both breakers (indoor and outdoor), and check the disconnect box near the outdoor unit. If all look fine, you likely have a failed capacitor, contactor, or control board.
Why does my AC breaker keep tripping?
Repeated breaker trips indicate a serious electrical issue — a short in the wiring, a failing compressor drawing too much current, or a ground fault. Do not keep resetting it. Call an HVAC technician to diagnose the root cause.
Is a clicking AC dangerous?
Clicking when the thermostat calls for cooling usually indicates a failed capacitor or contactor — not dangerous but needs repair. However, clicking combined with a burning smell suggests an electrical short that should be addressed immediately.