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“If you can test the capacitor you can test the disconnect.”
Photo Credit: iStock
A sudden AC failure during a hot spell can become a big problem fast, even when the culprit is a relatively small part.
That’s what happened to one homeowner after the outdoor unit kept running its fan while the compressor never started and only made clicking and humming noises.
In a Reddit post, the homeowner said a little troubleshooting with “the University of YouTube” led them to remove and test the capacitor, after which they concluded that the capacitor was “indeed dead.”
“My AC stopped working randomly today,” the OP wrote, discussing how the process began, which prompted them to check the outside unit.
That raised a second issue: whether the nearby pullout disconnect also needed to be replaced, since the homeowner said it “doesn’t look great.”
Replies mostly suggested not replacing the disconnect right away.
“If you are comfortable with it, I would suggest turning off the breaker and at least looking at the wire terminals under the plastic cover in the disconnect to see if they are loose or burned,” one commenter recommended.
Another put it more simply: “No, try just the cap first. 9.9999/10 disconnects are fine and last for years.”
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If you’re dealing with a similar issue, it can help to understand your repair options before paying for a service call.
If the issue turns out to be more serious than a simple part replacement, EnergySage can help you compare efficient heating and cooling solutions and connect you with vetted installers through its heat pump marketplace program — a useful way to understand your HVAC options and slash your energy bills with new, efficient HVACs.
A dead capacitor is often a relatively minor repair, but aging cooling systems can get expensive fast, especially during extreme heat. Even when the fix is straightforward, diagnosing the problem, finding the right part, and confirming everything is safe can push homeowners toward a full replacement.
Upgrading a heating and cooling system can lower utility bills and help protect against rising energy prices. Newer high-efficiency systems, especially heat pumps, can reduce wasted energy while improving comfort in both summer and winter.
Safety was another recurring theme in the discussion. Commenters said the disconnect should be checked carefully before any work is done.
“If you can test the capacitor, you can test the disconnect. Are you getting proper voltage? That’s all you need to know,” one commenter wrote.
Another added that homeowners should “verify that there is no high voltage passing through.”
Anyone troubleshooting the issue should first shut off power at the thermostat, breaker, and outdoor disconnect before opening anything.
If that feels like more than you want to handle, or if the unit is older and struggling, EnergySage can help you compare efficient HVAC paths before you commit.
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Symptoms such as a humming or clicking compressor alongside a fan that still spins often line up with a common failure, but they can also be a sign that a cheap fix won’t solve the larger problem.
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© 2025 THE COOL DOWN COMPANY. All Rights Reserved. Do not sell or share my personal information. Reach us at hello@thecooldown.com.

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