When summer heat sets in, nothing is more frustrating than an AC not cooling when you need it most. Every year, Postma Heating, Cooling, Plumbing and Electrical gets a wave of service calls from homeowners with the same complaint: the air conditioner is running, but the air coming out is warm.
One of the leading causes? A small but essential component called the capacitor.
The Role of a Capacitor in Cooling Your Home
The capacitor works like a burst of stored energy for your AC’s motors. There are two main types:
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Start capacitors – Give the compressor the power surge it needs to start running.
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Run capacitors – Keep the motor running smoothly through the cooling cycle.
When a capacitor fails, your AC may hum but never start, shut off unexpectedly, or simply blow warm air. That’s when you end up with an AC not cooling right in the middle of a heatwave.
Why Summer Heat Triggers More AC Problems
Hot, humid summer weather puts extreme stress on air conditioning systems. Capacitor failures spike during this season because of:
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Heat stress – High outdoor temperatures cause internal components to overheat and wear out faster.
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Heavy workload – Long cooling cycles mean capacitors are charging and discharging constantly.
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Age – Capacitors generally last 5–10 years, and older ones are more likely to fail under pressure.
According to the U.S. Department of Energy’s guide to common AC problems, regular maintenance is key to preventing these situations by spotting worn parts before they break.
Signs Your AC May Have a Failing Capacitor
If your air conditioner is blowing warm air or taking too long to start, the capacitor might be to blame. Watch for these signs:
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Weak or no airflow from vents
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AC shuts off randomly during operation
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Humming sound from the outdoor unit
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Bulging or leaking capacitor casing
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Burning smell near the outdoor unit
Any of these symptoms can lead to an AC not cooling — and running the system in this condition risks damaging the compressor.
How to Prevent Mid-Summer Breakdowns
While capacitors will eventually wear out, you can lower the chances of an AC emergency by:
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Scheduling annual AC maintenance in spring
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Keeping the outdoor condenser free from dirt and debris
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Avoiding sudden thermostat drops during extreme heat
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Replacing older capacitors before peak cooling season
Other Reasons an AC Might Not Be Cooling
Not all cooling problems are caused by capacitors. Your system could also be struggling due to:
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Low refrigerant from a leak
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Dirty evaporator or condenser coils
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Clogged air filter
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Faulty thermostat
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Compressor issues
Carrier’s troubleshooting guide for AC not working highlights that airflow restrictions, electrical faults, and sensor problems can also cause poor cooling performance.
Only a certified HVAC technician can confirm the cause of an AC not cooling and recommend the right repair.
Get Your Cool Back Fast
If your AC is not cooling, don’t wait for the problem to get worse. Capacitor failures are one of the most common issues we see every summer, but quick action can save you from costly repairs.
Whether you’re in Chatham-Kent or the surrounding area, Postma Heating, Cooling, Plumbing and Electrical can get your system running at full power again so you can enjoy a cool, comfortable home all summer long.
📞 519-354-9491
📲 226-702-2071
🔗 www.postma.ca
📧contact@postma.ca