This post overlaps with a fuller one: Signs Your Outside AC Unit Needs Repair, and What Each Means.
Most air conditioner failures in a Pasadena, CA home start at the outside unit, because that is where the compressor, the condenser fan, the capacitor, and the contactor live. When one of them stalls, the indoor blower keeps running and the house slowly warms up. This is the short version of what each symptom means and when it needs a licensed tech.
The signs, in the order we see them
- Silent outdoor unit, indoor blower running. Tripped breaker, pulled disconnect, failed capacitor, failed contactor, or a float switch indoors that shut the system down over a clogged drain.
- Fan hums but does not spin. Almost always a weak or dead capacitor, sometimes a seized motor. Do not spin the blade with a stick.
- Runs but the air is not cold. A condenser coil packed with dust after a windy week, a refrigerant leak, a compressor losing capacity, or a clogged filter indoors.
- New noises. Loud buzzing points at electrical parts, grinding at fan bearings, hissing at a refrigerant leak, and banging means shut it off now.
- Ice on the copper lines. Low refrigerant or restricted airflow. Turn the system off and let it thaw before anyone looks at it.
- Short cycling or a breaker that trips again after one reset. Leave it off and call.
What to check before you call
Thermostat on Cool and Auto, the breaker reset once, the disconnect pull-out in place, a fresh filter, roughly two feet of clear space around the unit, and, with the disconnect pulled, a gentle garden-hose rinse of the coil from the outside. Leave the electrical panel on the unit closed; the capacitor holds a charge with the power off.
When it is a tech's job
A hum with no spin, any ice, hissing, burning smells, repeated breaker trips, or a unit that still will not cool after the filter and coil are clean. Capacitors and contactors are short AC repair visits. Compressors are not, which is why the early signs matter, and why a spring HVAC maintenance visit before the first heat wave catches most of them. If the unit is old enough to run on R-22, whose production and import ended in 2020, ask for a replacement quote next to the repair quote.
Our diagnostic visit is $69, told to you before booking and credited toward the work. Boost Services Heating and Cooling answers at 818-277-5056 or contact us here.
The full guide: Signs Your Outside AC Unit Needs Repair, and What Each Means
Written with AI assistance by Boost Services, Heating and Cooling team, and reviewed by our licensed technicians before publishing. Boost Services Heating and Cooling, C-20 #1119892.