Why Do Your Lights Flicker When AC Turns On?

Welcome to another post from your friendly neighborhood contractors at Anderson Air! 

Today, we’re diving into a strange phenomenon you may have encountered in your home: lights flickering when your air conditioning turns on. If you’ve ever experienced this, it can seem odd and perhaps a little spooky. Don’t worry though – it’s actually quite common in many households. 

Typically, if your lights flicker when your AC system kicks on, it’s not an issue. That said, if the flickering is severe, it may indicate a problem with your electrical system. 

Keep reading and we’ll shed a little light on this electrical mystery for you. 

Understanding your AC system 

At Anderson Air, we believe in empowering our customers with knowledge – we want to help you understand your system better. Before we explain why your lights flicker when your AC turns on, let’s look at  how an air conditioning unit operates and the key electrical components involved. 

Setting your thermostat may feel like a simple dial shift or button click, but it’s actually the beginning of a chain-link reaction in the system. 

The change triggers the AC unit’s compressor, which functions like the heart of the system. When it springs into action to pump refrigerant throughout the unit and kickstart the cooling process, it draws a lot of electrical power. This sudden surge in demand can often cause the lights in your home to flicker slightly.

Flickering lights are perfectly fine if: 

  • They only flicker once, and for a brief moment 
  • The lights only dim slightly and then return back to normal 

Due to the power required to start your cooling system, minor flickering or dimming is normal and shouldn’t worry you. 

When should I be concerned? 

The occasional light flicker when your AC unit revs up is typically harmless and a normal part of your home’s electrical system’s give and take. However, constant or very frequent flickering could signify a more serious problem. 

Here are some signs and symptoms that might indicate a problem with your HVAC system or electrical supply:

  • They continue to flicker and turn on an off repeatedly 
  • They dim more than 50% of their brightness or go out completely 
  • You hear a sizzling or crackling accompanied with it
  • In addition to the lights, other appliances are affected 

If you notice any of these when your AC starts up, it’s often an indication that something is wrong. Contact an HVAC technician (like the Anderson Air pros!) to take a look at your system. 

Common problems and solutions 

If you’re experiencing any of the issues listed above, here is a list of some common causes and solutions. 

Damaged wiring or loose connections 

If you notice consistent flickering or your lights turning on and off, you may have some damaged wiring that needs attention. As the electrical current travels through the circuit, loose or damaged wiring can disrupt the flow, causing an intermittent supply to your lights. 

This often looks like your lights blinking on and off and becomes especially noticeable when other major appliances or systems, such as your air conditioning, draw a substantial amount of power.

Weak or broken capacitor 

Another potential culprit behind your flickering lights when the AC turns on could be a weak or broken capacitor within the unit itself. 

So, if you notice that your lights dim significantly or shut off completely, this is likely the issue. 

Since the AC unit needs a burst of power when starting up, the system’s capacitor functions as a battery that stores the extra energy that the unit can use. When it starts the capacitor draws a lot of electrical energy. However, if it’s weak or faulty, it can cause imbalances in the load and you will see a decrease in power to your other appliances, like your lights, for example. 

Over time, the power bursts but strain on a faulty capacitor and can lead to more frequent or persistent flickering, and potentially even lead to the premature failure of the AC unit. Contact a professional to avoid further damage to your system. 

An overloaded circuit

An overloaded circuit is another potential cause for flickering lights. Your home’s electrical system is made up of circuits which bear what’s called “loads” or appliances drawing power. Just like we have a physical limit on how much load or weight we can carry at once, if there are too many appliances pulling electricity from the same circuit, it can max out the circuit’s capacity, leading to an “overload”. 

This overload can cause a temporary voltage drop, which may result in noticeable dimming of the lights and a sizzling or crackling noise. 

It’s important for your power loads to be balanced evenly throughout your home to avoid this. If you hear crackling and see severe dimming, contract a professional to evaluate your home’s electrical set up. They’ll check your system and work out a way to even things out. 

The age of your electrical system vs the age of your unit

The age of your electrical system compared to the age of your AC unit is an important thing to consider. Older electrical systems were designed for lower power consumption patterns and may struggle to handle the power demand of modern, high-efficiency AC units. 

When your AC unit powers up, the sudden demand for electricity can result in a drop of power to other appliances, including your lights. But, if your home’s electrical system is older and you’re experiencing persistent light flickering, it could indicate that your electrical system is struggling to keep up with your AC unit’s power requirements. 

Get your system checked by a licensed electrician or HVAC professional. They’ll take a look at your system’s capacity and let you know if you need an upgrade. 

How can I prevent my lights from dimming when my AC starts up?  

Since most heating and cooling systems draw a lot of power when they start up, it’s difficult to prevent it completely in the average home. It’s also not necessary to completely prevent it if it’s minor. 

However, if you’re noticing any of the severe signs we mentioned above, give us a call and we’ll help you out. We’ll give you information about your system and what it needs to work at its best. 

If you’re not sure, call the pros at Anderson Air to take a look. 

At Anderson Air, your comfort is our priority, and we’re here to ensure your HVAC system works efficiently and effectively. So remember, even if your lights flicker, it’s usually a normal part of your home’s electrical dance. 

We understand – it can be hard to tell and judge what’s “normal” for your home system. But don’t worry; we can help. If you ever have concerns about your HVAC system, or if you’re ready for a check-up, don’t hesitate to contact us. 

Our professional team is trained and ready to assist you. So why wait? Reach out to us for professional, friendly service today! 

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