Emergency
AC Won’t Turn On?
What to Check Before Calling
Your air conditioner is completely unresponsive — no fan, no compressor, nothing happens when you adjust the thermostat. Before calling a technician, there are several things that resolve this about 25% of the time.
AC runs but air isn’t cold?
That’s a different issue — see AC Not Cooling instead.
Common Causes
A completely dead AC usually comes down to one of these five issues.
1
Tripped Breaker
The most common and simplest cause. Power surges, lightning, or a momentary overload can trip the AC breaker. Check your electrical panel first. AC systems often have two breakers — one for indoor, one for outdoor. Both must be on.
2
Thermostat Issue
Dead batteries (battery-powered models), blank display, or thermostat that lost its programming. Some thermostats have a small breaker or fuse inside. Try replacing batteries first — this is free and takes 30 seconds.
3
Safety Switch Tripped
Modern AC systems have safety switches that shut the system down when something is wrong. Common: condensate drain overflow switch (drain is clogged, water backing up), high-pressure switch, or float switch in the drain pan. These are protective — don’t bypass them.
4
Failed Capacitor
Capacitors store the electrical charge needed to start the compressor and fan motors. They’re one of the most common AC parts to fail, especially after a heat wave when the system runs hard for days. You may hear a clicking or humming from the outdoor unit.
5
Outdoor Disconnect Off
There’s usually a disconnect box on the wall near the outdoor unit. Landscapers, painters, or anyone working near the unit may have switched it off. It looks like a small metal box with a pull-out handle or switch.
Safe Checks You Can Perform
Check the thermostat. Is the display on? Try fresh batteries. Make sure it’s set to COOL with temp below room temp. Try turning it off, waiting 5 minutes, then back on.
Check BOTH breakers. Go to your electrical panel. Find the AC breakers (usually labeled “AC” or “Air Handler” and “Condenser”). If tripped, flip fully to OFF then back to ON. If it trips again immediately — stop and call.
Check the outdoor disconnect. Find the metal box on the wall near the outdoor unit. Make sure the handle is in the ON position or the pull-out fuse block is seated correctly.
Check the condensate drain. If your system has a safety float switch, a clogged drain line will shut everything down. Look for water pooling near the indoor unit or in the drain pan. Clear the drain if accessible.
Check the furnace/air handler power switch. There’s often a light switch on the wall near the indoor unit that controls power. It’s easy to flip off accidentally — check that it’s ON.
Signs You Need a Professional
Breaker trips immediately when reset — electrical short circuit or ground fault. Do not keep resetting. Call immediately.
Outdoor unit hums or clicks but won’t start — failed start capacitor or contactor. The compressor is trying to start but can’t. Common repair, usually $150–$350.
Burning smell from indoor unit — turn off the system immediately. Could be a failing motor, overheated wiring, or electrical component. This is a potential fire hazard.
All checks pass but system still dead — could be a control board failure, blown transformer, or internal fuse. Requires a technician with diagnostic equipment.
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Related Problems
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Frequently Asked Questions
Most common causes: tripped breaker, dead thermostat batteries, outdoor disconnect switched off, or a safety switch triggered by a clogged condensate drain. Check all of these before calling — about 25% of the time, it’s one of these simple fixes.
A humming outdoor unit that won’t start usually means a failed start capacitor or contactor. The compressor is receiving power and trying to start but can’t get going. This is a common and relatively affordable repair ($150–$350). Don’t leave it humming — it strains the compressor.
Yes — a breaker that trips repeatedly indicates an electrical fault: short circuit, ground fault, or a component drawing too much current. Do not keep resetting it. Each reset exposes the wiring to the fault condition again. Call a licensed technician to diagnose before resetting again.
AC Won’t Turn On?
Same-day AC diagnosis and repair. We carry capacitors, contactors, and common parts on our truck for faster fixes.
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