The Most Common AC Failures (and What Causes Them)
When Your AC Quits, It Usually Has a Reason
Air conditioners rarely fail without warning. Most breakdowns we are called out for across the Portland metro trace back to a handful of recurring culprits — and many of them give off signs days or weeks before the system finally stops cooling.
This guide, part of our cooling hub, runs through the failures we see most. Knowing what you are looking at helps you describe the problem clearly and decide how urgently you need AC repair. You can also reach us any time through our main site.
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Six Failures We See Again and Again
Each of these has telltale symptoms. Some are minor, some are serious — a free diagnostic tells you which.
Refrigerant Leaks
Weak cooling, ice on the lines, or a hissing sound. Low refrigerant always means a leak — it never simply runs out — and needs professional repair.
Failed Capacitor
A humming unit that won't start, or a fan that won't spin. Capacitors are a frequent, fixable failure — and a common cause of no-cool calls.
Compressor Trouble
Hard starts, breaker trips, or no cooling at all. The compressor is the costliest part, so catching strain early really pays off.
Frozen Evaporator Coil
Ice on the indoor unit and warm air from the vents. Usually caused by dirty filters or low airflow choking the coil.
Blower Motor Failure
The system runs but little air comes out. A worn motor or bad capacitor in the air handler is often the cause.
Thermostat & Controls
The cheapest failure of all — a miscalibrated or dead thermostat can mimic a major breakdown when nothing else is wrong.
Before You Call, Read These
Start with the simple stuff: check the thermostat is set to cool, replace a dirty filter, and confirm the breaker hasn't tripped. If those are fine, warm air usually points to low refrigerant or a compressor issue, both of which need a professional. A free diagnostic confirms it quickly.
That is a classic sign of a failed capacitor — the part that gives the motor its starting jolt. It is one of the more affordable and common repairs we do. Don't keep cycling the unit, though, since that can stress the compressor.
Turn the system off and let it thaw. Ice usually means restricted airflow from a dirty filter or coil, or low refrigerant. Running it while frozen can damage the compressor, so it is worth getting checked before you keep using it.
Absolutely. A dead battery, loose wire, or miscalibrated thermostat can stop a perfectly healthy system from cooling. It is one of the first things we rule out — and one reason a quick diagnostic beats guessing at expensive parts.
Most of them start small. Annual maintenance, clean filters, and a clear outdoor unit prevent the majority of the breakdowns on this page. Our cooling hub covers prevention in depth, and you can always reach us through our website.
Where to Go Next
Talon Mechanical
Locally owned HVAC serving Gresham, Portland, and the surrounding metro. Meet the team.
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Don't Push a Failing AC Through Summer
If anything on this page sounds familiar, the smart move is a quick diagnosis before a small fault becomes a big one. Talon Mechanical offers a free onsite diagnostic and a 30-day guarantee on qualifying repairs.
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