AC Keeps Tripping the Breaker? Why It Happens and What to Do
The breaker for the AC trips when it starts, after it runs a while, or on hot afternoons.
By Mark Curant·Updated
Most likely causes
- A dirty outdoor coil or blocked airflow making the compressor draw more current
- A failing capacitor, so the motors struggle to start
- A compressor that is hard to start or failing
- A failed outdoor fan motor
- A short in the wiring or a motor (trips instantly)
- A worn breaker or a loose connection at the panel
Before you open anything
Turn the system off at the thermostat, then switch off power at the breaker and at the disconnect beside the outdoor unit. Never touch the capacitor, even with the power off: it can hold a dangerous charge. Refrigerant work is for licensed technicians only. Reset a tripped breaker once; if it trips again, leave it off.
Never replace the breaker with a larger one to stop it tripping. Breakers are sized to the wiring and the unit; a bigger one lets the wires overheat. Panel work is for a licensed electrician.
Check these first (free, 5 minutes)
- Which breaker: the outdoor unit, or the indoor unit (air handler or furnace)?
- When it trips: the instant you reset it, when the compressor starts, or after running for a while on hot afternoons.
- Look at the panel and the disconnect beside the outdoor unit: scorch marks, a burning smell or a hot breaker mean stop and call.
- Outdoor coil and filter: matted fins outside or a clogged filter inside make the motors work harder.
Causes, signs and repair costs
Dirty outdoor coil or blocked airflow
DIY or proTrips after running a while, mostly on hot afternoons; fins matted or plants crowding the unit
Typical cost: $0 DIY rinse, $100–$300 pro cleaning
Failing capacitor
ProTrips as the outdoor unit tries to start; humming before it trips
Typical cost: $150–$400
Hard-starting or failing compressor
ProTrips the moment the compressor starts; lights dim; system over about 10 years old
Typical cost: $30–$80 hard-start kit part plus labor; $1,500–$3,000 for a compressor
Failed outdoor fan motor
ProFan doesn't spin, unit gets very hot, then the breaker trips
Typical cost: $400–$800
Short in wiring or a motor
ProTrips instantly every time you reset it
Typical cost: $150–$1,000 to find and repair
Worn breaker or loose connection
ProBreaker warm, buzzing or tripping with no other symptom; the system runs fine on a tester's meter
Typical cost: An electrician's visit plus the breaker
Indoor blower strain
DIY or proThe indoor unit's breaker trips; clogged filter or a failing blower motor
Typical cost: $5–$20 filter, $500–$1,200 blower motor
| Cause | Signs | Who fixes it | Typical cost |
|---|---|---|---|
| Dirty outdoor coil or blocked airflow | Trips after running a while, mostly on hot afternoons; fins matted or plants crowding the unit | DIY or pro | $0 DIY rinse, $100–$300 pro cleaning |
| Failing capacitor | Trips as the outdoor unit tries to start; humming before it trips | Pro | $150–$400 |
| Hard-starting or failing compressor | Trips the moment the compressor starts; lights dim; system over about 10 years old | Pro | $30–$80 hard-start kit part plus labor; $1,500–$3,000 for a compressor |
| Failed outdoor fan motor | Fan doesn't spin, unit gets very hot, then the breaker trips | Pro | $400–$800 |
| Short in wiring or a motor | Trips instantly every time you reset it | Pro | $150–$1,000 to find and repair |
| Worn breaker or loose connection | Breaker warm, buzzing or tripping with no other symptom; the system runs fine on a tester's meter | Pro | An electrician's visit plus the breaker |
| Indoor blower strain | The indoor unit's breaker trips; clogged filter or a failing blower motor | DIY or pro | $5–$20 filter, $500–$1,200 blower motor |
Typical U.S. installed prices in 2026. Most repairs also carry a service call fee of $75–$200, often credited toward the repair. See AC repair costs in 2026 for the full list.
Step by step
- 1
Reset once, properly
Turn the thermostat off. Push the tripped breaker firmly to Off, then back to On. Wait 5–10 minutes before setting the thermostat to Cool, so the compressor doesn't start against high pressure.
- 2
Watch when it trips
Instantly on reset points to a short: leave it off. At start-up points to the capacitor or compressor. After a while on hot afternoons points to a dirty coil, a failing fan motor or airflow. Tell the technician which it was.
- 3
Clean the coil and replace the filter
With power off at the disconnect, rinse the outdoor coil from the outside and clear plants back 2 feet. Fit a new indoor filter. These are the only causes you can fix yourself.
- 4
If it trips again, leave it off
A breaker trips to protect the wiring from overheating. Resetting it over and over can damage the compressor and, in the worst case, start a fire. One reset, then call.
- 5
Check the breaker size, not by guessing
The outdoor unit's nameplate lists the maximum fuse or breaker size (often "MAX FUSE/BKR"). The breaker should not be larger than that. Never fit a bigger breaker to stop the trips; that only removes the protection.
Call a technician if
- It trips again after one reset
- It trips the instant you reset it
- A burning smell, scorch marks, or a breaker that feels hot or buzzes
- The lights dim and it trips as the compressor starts
Red flags on a quote
- A new system quoted before the capacitor, fan motor and compressor have been tested
- A larger breaker offered as the fix
- For a failed compressor on a system over about 10 years old, compare the quote with replacement before agreeing
Facing an expensive repair on an older system? Run it through the repair vs replace calculator, or read the $5,000 rule.
Frequently asked questions
Why does my AC keep tripping the breaker?
Most often because the outdoor unit is drawing more current than it should: a dirty coil or blocked airflow on hot days, a failing capacitor that makes the motors struggle to start, or a compressor that is wearing out. A breaker that trips instantly on reset usually means a short circuit.
Is it safe to keep resetting the AC breaker?
No. Reset it once. If it trips again, leave it off and call a technician. The breaker is doing its job by cutting power to something that's overheating or shorted, and repeated resets can damage the compressor or start a fire.
Can a dirty filter cause the AC breaker to trip?
It can strain the indoor blower motor, which can trip the indoor unit's breaker. A dirty outdoor coil is the more common cause of the outdoor unit's breaker tripping, especially on hot afternoons.
What size breaker does my AC need?
The outdoor unit's nameplate lists the minimum circuit ampacity and the maximum fuse or breaker size. The breaker must not exceed that maximum. If you think the breaker is the wrong size, have an electrician check it against the nameplate and the wiring.
Related problems
Outdoor unit not running
The indoor fan blows but the outside unit is silent, humming or its fan is still.
AC won't turn on
Nothing happens when you lower the thermostat: no fan, no outdoor unit.
AC not working after a power outage
Power is back on, but the AC won't start or doesn't cool.
Fixed it? Check what it costs to run
If your system is old enough to keep breaking, compare its running cost with a new one before the next repair.
Open the SEER savings calculator