AC Unit Humming or Buzzing But Not Turning On (Easy Fix!)

In hot climates, air conditioning units are a must. They’re as vital as heating systems in colder climates.

Mainly, AC units operate for years without posing any problem; however, they also experience issues like other electrical appliances.

So, is your air conditioner buzzing but not running? If you encounter these or other issues, don’t panic!

Keep reading to know more!

Why Is My AC Unit Humming Or Buzzing But Not Turning On?

Does your air conditioning system makes a humming or buzzing sound but isn’t turning on? If so, there can be many reasons. First thing first, this indicates you might have a defective capacitor.

Capacitors provide that additional electricity jolt required to get AC motors started or/and to operate continuously. Some clear signs of faulty capacitors include but are not limited to:

  • Mushroomed ‘swollen’ top
  • Capacitors that are rusted or corroded at the bottom
  • Fluid leaks from any component of a capacitor

If the capacitors attached to the fan motors go wrong, chances are the fan won’t start. This prevents the AC system from heat transfer from indoors to outdoors (this explains why the air from the vents is hot rather than cool).

So, if the capacitors are broken, the AC fan motors don’t have sufficient jolts to move. Want a smooth fix for faulty fan motor capacitors? Follow these steps:

  1. Turn on your air conditioning system
  2. Grab a thin, long object (a screwdriver or a stick will do fine)
  3. Use it to thrust fan blades within the compressor

This will provide the ‘jolt’ that the AC fan motor requires to gain much-needed speed. Don’t forget to take precautionary measures before doing it so that no one will get hurt.

Note: If the fan still doesn’t run, chances are you might have a faulty fan motor. If that’s the case, call your HVAC professional technician and have a replacement.

Related Article Unusual Sound From Your AC

AC Buzzing But Not Turning On

How To Tell That The AC Capacitor Is Bad?

Homeowners can usually fix most AC problems; however, if you’ve got a faulty capacitor, you’ll need professional assistance.

Wondering how to tell if the AC capacitor experiences failure or is faulty? Here are a few common signs of faulty AC capacitor:

Related Article Cost To Replace AC Capacitor

AC Fan Is Not Running

A faulty or failing AC capacitor might be to blame if the AC fan isn’t running at all, even when it’s switched on.

To check whether the fan failure is because of a bad capacitor, here’s what you need to do:

  • Walk to where your AC condenser system is located
  • If the system is switched on and the AC fan isn’t running at all, use a branch to spin fan blades
  • If the unit starts after that little push, the problem lies with the capacitor
AC Fan Not Running

Delayed Cooling

To cope with the searing heat of summers, many homeowners turn to their air conditioning systems to get relief from the outdoor heat.

If you’ve got an air conditioner that’s taking a long time to cool down the space or doesn’t blow the cool air at all, it might have a defective component.

If the air filter and fan of the unit work properly, chances are the problem lies with the AC thermistor, capacitor, or electronic control panel.

AC Starts Shutting Off At Random

As AC capacitors are responsible for powering your air conditioning system, the unit will shut off randomly if there’s anything wrong with AC capacitors.

This typically means that capacitors are no longer offering adequate energy to your AC system, as they’re no longer keeping enough load to sustain overall operations.

On the whole, you’ll have to replace capacitors as quickly as possible. However, before replacing the capacitor, check how long it can last further.

The AC Is Refusing To Turn On

As mentioned earlier, the AC capacitors are solely responsible for jump-starting your air conditioner by providing it with a massive jolt.

However, if the system doesn’t switch on immediately, it means you’ve got a failing or bad AC capacitor.

This means that the AC capacitors require more power to get things done. It might be building adequate charge at the start to turn your AC system on.

Typically, AC capacitors have failed in such situations and cannot get fixed, which means you’ll have to replace them.

Higher Energy Bills

Believe it or not, if you’re getting high energy bills every month, it’s an indication of a failing air conditioner capacitor.

Most homeowners don’t understand that a rise in the overall cost of energy bills might be attributed to the failing AC capacitors. If your unit’s capacitor is defective or failing, the AC system will need to work much harder to cool down your space.

This means the unit will consume more power, which automatically will show up in your monthly utility bills.

Remember that AC capacitors will not operate properly for a single cycle and fail afterward. As a result, their performance will decline steadily, leading to higher bills.

Hear Strange Humming Or Buzzing Sound

Here’s the thing: every homeowner should get familiar with their AC unit’s sound. It’s increasingly helpful. This way, you’ll know which sound indicates usual operations and which means a failure.

Call your professional HVAC technician right away if the system makes strange sounds. For example, if the sound you hear resembles buzzing or humming and it’s coming from within the unit, there’s a good chance that it means you have got a faulty capacitor.

The capacitor works hard and overtime to meet your needs, hence the weird buzzing or humming sound.

The AC Unit Is Extremely Old

An AC capacitor loses its energy as it gets older. If your AC system is older, all components have also aged with it, including the capacitor. As a result, older capacitors lose their ability to operate.

If that’s the case, you should contact your technicians and replace the capacitor. It’s best to replace the entire air conditioning unit if the system is way older.

Replacing components on older units will cost you more money, time, and effort.

Related Article Buying Air Conditioner Parts

How To Fix The AC Unit Humming Or Buzzing But Not Turning On?

Fix AC Humming But Not Turning On

Always start with preventive measures; however, you’ve got two choices to fix your air conditioning system now that you’re already here.

Either choose a quick fix or go for the long-term solution; the choice is entirely yours to make. Without further ado, here are two feasible ways to fix AC humming but not switching on:

Quick Fix (Manual Spinning)

The band-aid solution is quite basic as it includes manual spinning. But, first, you’ll have to start the AC fan manually.

To do this, grab a screwdriver or something else that you can use to spin your AC unit fan. You’ll be sorting out the hard-start issue by offering the power system needs to get going.

Remember that this ‘rotation’ is just a short-term maneuver and shouldn’t be done routinely. Instead, please take it as an urgent intervention meant for kick-starting your AC fan’s motor.

Also, take the necessary preventive steps while spinning the fan. This is highly crucial because you can either damage your air conditioning system’s fan or get exposed to shocks. Handle all-electric appliances carefully.

As for capacitors, even limping ones can be highly lethal. This is because they carry a significant amount of energy with them.

In addition, they’re designed to emit energy in snaps, which means even dysfunctional and old capacitors can be extremely dangerous.

Long-Term Solution (Capacitor Replacement)

If the capacitors connected with fan motors are weak and won’t run the fan, you require a long-term solution: capacitor replacement.

Remember, not everyone can handle capacitors. You require the proper technical understanding and tools to identify which capacitor you’ll need for the unit.

The procedure is simple, provided you know what you’re up to:

  1. Disconnect the air conditioning system from the power source
  2. Take out the panel so you can easily reach the capacitor
  3. Check the capacitance and voltage ratings and order the replacement
  4. Discharge the current capacitor and eliminate it
  5. Replace it with the new one.
  6. Before turning on the air conditioning system, double-check the work

If the air conditioning unit is quite old (probably eight years and above), consider replacing your entire AC system, particularly if it’s giving you enough trouble lately.

How To Prevent The AC Capacitor From Going Bad?

Remember, prevention is better than cure! Their ability to operate appropriately directly links with the unit’s age in terms of capacitors.

Nevertheless, there’s a range of things that you can perform to prevent the AC capacitor from going bad.

Don’t Overdo The Unit With Additional Cooling

Here’s the thing: the more complex the AC system operates, the more the chances of capacitor burnout. So if you want to ensure your AC capacitors last longer, don’t overdo them with extra cooling.

In addition, invest in power-efficient cooling methods such as insulation and blackout curtains. Also, keep your thermostat a bit higher than average if you can handle it.

Consider Installing HVAC Surge Protectors

We know that electrical surges from hurricanes, cyclones, and other storms (also from heavy grid use) can cause electronic components to malfunction.

It includes the HVAC kit as well. Consider having surge protectors for your AC systems to ensure that your air conditioning unit doesn’t get affected by the surge.

Don’t Use The System Excessively

Remember, the less you’ll use your air conditioning system, the less strain you’ll place on the capacitor – it’s that simple! So, always use it when necessary.

People Also Ask (FAQ)

How long does an AC capacitor usually last?

Most AC capacitors are meant to last about 15 to 20 years. However, several factors can cause capacitors to wear quicker than expected. For example, if the AC unit cycles much faster than average, the capacitor is either undersized or made from complex components, reducing its life span significantly.

Can you run the air conditioner with a bad capacitor?

If the AC capacitors have failed or starting to fail, don’t run the air conditioner no matter what. If you run it with a bad capacitor, it will further damage your system and cause you to replace bigger pricier parts or even the entire unit.

Can a bad capacitor be repaired?

Luckily, if you detect a capacitor problem on time, your HVAC technician will swap it out quickly for the new one without any effect on the AC unit. But, if you ignore bad AC capacitors, you might end up replacing your entire air conditioning system.

Can I replace the AC capacitor myself?

Yes, you can! Though replacing AC capacitors are easy and can smoothly be done with suitable materials and tools, you should still let the professionals do it. This is primarily because capacitors are meant to store an electric current, and there’s a high chance that you can get a shock if you do it by yourself.

How much does it cost to replace a bad capacitor?

AC capacitors will cost you anywhere between $130 and $260. Though the cost varies based on several factors such as model type, brand, and whether it’s a dual or single run, the average price to replace bad capacitors is approximately $180. Some AC capacitor costs can go up to $300 to $400.


Air conditioners provide an efficient and effective way to cool down your space, even in hot climates. But, like any other electrical appliance, air conditioners also face problems.

If the outdoor air conditioning unit is buzzing or humming, but the AC fan isn’t working, it means you’ve got a faulty or lousy capacitor!

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Josh Mitchell

Josh Mitchell

My name is Josh and I am obsessed with DIY and improving my family home. HVAC topics can be tricky for homeowners so I decided to share my knowledge on the subject. When I am not working on DIY projects, you can find me at the beach or my local coffee shop.