Air conditioner not cooling
Ranked from 2,400 repairs on split-system condensers with this symptom. Narrow it below and the ranking recomputes.
Before you start — Kill the power, then discharge the capacitor electrical · refrigerant safety
Pull the disconnect at the outdoor unit AND switch off the breaker. A run capacitor holds a dangerous charge for a long time after the power is off — discharge it across an insulated resistor before you touch the terminals, and never bridge them with a screwdriver. Anything that opens the sealed refrigerant system is EPA-608 licensed work.
Narrow it down
My AC unit hums but the fan doesn't spin — what's wrong?
A hum with no rotation is the run capacitor's signature failure — about 76% of these repairs end with a new capacitor. The motor is being asked to start and has no starting torque. Kill the power and discharge the capacitor before touching anything: it holds a dangerous charge long after the disconnect is pulled.
-
Most likely — 76%
TRD-45550
45+5 µF 440V Dual Run Capacitor
320 in stock · ships today
$18.40 Pro price $15.64 save $2.76 (15%)76% of matching repairsHum, no spin, is the textbook dead run capacitor: the motor has voltage and no phase shift to start against.
Try this first: Look for a domed or leaking top first — free, and it confirms the diagnosis outright.
-
Also check — 14%
CFM-1052
1/5 HP Condenser Fan Motor, 825 RPM
22 in stock · ships today
$128.50 Pro price $109.23 save $19.27 (15%)14% of matching repairsA seized bearing hums too. Spin the blade by hand with the power off — if it is gritty or locked, a new capacitor won't save it.
The remaining 10% of matching repairs resolved without a replacement part — a filter, a reset or a thermostat setting.
Verify against your model
We ranked these from the symptom. Your model number turns a ranking into a verdict.
Where's my model number? (photo guide)Not sure? Talk to a tech
Send a photo of your rating plate and a real tech confirms the part before you buy it. Free, about 10 minutes.
Ask a tech — free