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
Most likely parts ranked from 2,400 repairs
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Also check — 44%
TRD-45550
45+5 µF 440V Dual Run Capacitor
320 in stock · ships today
$18.40 Pro price $15.64 save $2.76 (15%)44% of matching repairsAn outdoor unit that hums but won't spin is a failed run capacitor more often than every other cause combined. A domed or leaking top confirms it — but a capacitor can drift far out of tolerance while looking perfect.
Try this first: Look before you buy: a domed, split or leaking top is a free diagnosis. If you have a meter, anything more than 6% under its rating is done.
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Also check — 21%21% of matching repairs
Burnt, pitted or welded contacts stop the compressor and fan getting power. If the contactor chatters, buzzes or the contacts look cratered, replace it.
Try this first: Free check: with the power off, press the contactor plunger in by hand and look at the contact faces.
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Also check — 16%
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%)16% of matching repairsIf the compressor runs but the top fan doesn't — and the capacitor tests good — the fan motor has failed. It will usually be hot to the touch with a stiff or notchy shaft.
Try this first: Spin the fan by hand with the power off. Gritty or seized is the motor; free-spinning points back at the capacitor.
The remaining 19% of matching repairs resolved without a replacement part — a filter, a reset or a thermostat setting.
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Ask a tech — freeCommon questions about this symptom
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.
See the parts for this →My outdoor AC unit doesn't run at all — what's wrong?
A condenser with no signs of life is usually not getting power to the compressor and fan: the contactor accounts for about 48% of these repairs. Check the disconnect and the breaker first — both are free — then look at the contactor's contact faces. A failed capacitor (22%) can also leave the unit silent rather than humming.
See the parts for this →My AC runs but the air isn't cold — what's wrong?
This one usually isn't a part. A clogged filter, a dirty condenser coil, a blocked return or a low refrigerant charge account for most of these — and refrigerant work is EPA-608 licensed, so it is not a DIY repair. Change the filter, wash the outdoor coil, make sure nothing is blocking the returns, and check the line set for ice before you buy anything. If it is still not cold, the charge or the metering device needs a licensed tech.
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