THE COOL GUYS BLOG

MY A/C DOESN’T TURN ON – IT JUST MAKES A BUZZING NOISE

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Scenario: Only warm air comes out when your A/C thermostat clicks on.

When you check your outside unit you notice that the outdoor unit is humming like normal but the fan is making a buzzing noise and it isn’t spinning.

What is the problem?

It could mean you have a bad fan capacitor when your outdoor A/C unit is humming and the fan isn’t running.

There’s a short-term fix you can do that’ll keep you cool until you can get your capacitor replaced.
We’ll give you that little trick shortly, but first, what exactly is a capacitor and what does it do?

A capacitor is…

A capacitor acts like a battery and stores large amounts of energy.  It is a small, cylinder-shaped metallic object and sits on the side of your outdoor unit.

Capacitors kick-start the compressor, the outdoor fan motor, and the blower fan (indoor unit fan).

Large appliance motors use up to 5 or 6 times more energy to start than they need when running. Capacitors offer that extra burst of electricity needed to get motors started.

So why do capacitors fail?

Just like batteries, capacitors weaken and lose their ability to hold an electrical charge over time. And then high temperatures and voltage surges can shorten a capacitors lifespan.

Some visual signs of a bad capacitor include:

  • A swollen, puffed out top
  • Corrosion or a rusted out on bottom
  • Fluid leaking from any part of the capacitor

When the capacitor connected to your fan motor goes out, the fan will not start. This stops your unit from removing the heat from inside your home and explains why the air coming from your vents is warm instead of cool.  See A/C Basics to learn how your air conditioner system works.

A short-term work around for a bad capacitor

Need a quick temporary fix for your fan motor capacitor?

Turn on the A/C unit.  Then take a long, thin object like a stick or screwdriver and use it to push the fan blades that are on top of the compressor.

This should produce the “kick” the fan motor needs to get up to speed. Be careful and take safety precautions when doing this so that nobody gets hurt.

Note: if this doesn’t get your fan running, you could have a bad fan motor and will need to have it replaced by a professional.

The long-term solution for a bad capacitor

If the capacitor connected to your fan motor is weak or has finally died and won’t start your fan, you need to have a professional replace it as soon as possible.

What can happen if it is not replaced?

When a capacitor goes bad, the motor it is connected to will still try to come on but most of the time the motor won’t be able to start on its own. This stalling can cause the motor to burn out which can lead to a more expensive repair.

The sooner you replace the capacitor, the more money you will save yourself in the long run.

Note: Although it is possible to replace a capacitor on your own, we don’t recommend it unless you have experience working with the electrical components of your air conditioner. 

Need an A/C tech to replace your capacitor?

Are you ready to get your air conditioner running properly?

Do you live in the San Antonio area?

Just call Cool Guys at (210) 534-2665 and schedule your appointment today. We’ll send a professional out to diagnose and repair your A/C unit in no time.

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