Why Do My Lights Dim When My AC Comes On?

Do your lights dim every time your air conditioner starts up?

It may be bothersome, but the good news is that this isn’t necessarily a cause for concern.

Your AC requires a lot of electricity to start up. So, when it kicks on, it’s temporarily draining electricity from other appliances like your lightbulbs. That’s why your lights briefly lose juice when your AC starts.

For the most part, this is a normal occurrence if:

  • Your lights dim only for a brief second or less
  • Your lights lose only about 5% of their brightness

On the other hand, dimming lights can be a sign of a larger (and possibly dangerous) electrical problem.

Wondering which is the case for you?

We’ve listed some problems that can cause your lights to dim when your air conditioner starts. Read on to see if you have any of the symptoms of these bigger issues.

Problem: Damaged or loose wires

Symptoms: Lights turn on and off rapidly at AC start up, wiring may be discolored/charred/ashy.

If you have a damaged or loose wire, it is most likely causing some current loss to your lightbulb. Add this to the voltage drop that occurs when your AC initially kicks in and the current loss could be enough to cause your lights to dim or even flicker temporarily.

The fix: If you think you have a loose connection, call a professional to find and repair your wiring.

Problem: Damaged or weak capacitor

Symptoms: Lights lose up to 30-40% of their brightness when the AC starts, compressor may have difficulty starting.

Your capacitor acts like a battery and gives your compressor motor the extra burst of power it needs to start.

But over time, capacitors can lose their ability to store energy.

When this happens, the AC drains more voltage from other appliances to start the compressor motor, causing the lights to temporarily lose brightness.

The fix: You’ll need a professional to examine your capacitor and replace it if needed. You can also ask them about installing a hard start kit.

A hard start kit feeds your compressor extra energy at start-up. This preserves the life of your compressor and should prevent your lights from dimming.

Problem: AC is sharing a circuit with lights/other appliances

Symptoms: A crackling/buzzing/sizzling sound accompanies the dimmed lights, lights may flicker or go out completely, Circuit breaker may trip.

The National Electric Safety Code requires that all major appliances have their own dedicated circuit. This includes your air conditioner. If other appliances are on the same circuit as your AC, they’re most likely overloading it.

Overloaded circuits are more common in older houses that were not designed to withstand the amperage of modern air conditioners. However, it can happen anytime there is a large number of high voltage appliances on one circuit.

This is a dangerous problem as overloaded circuits can cause fires and electric shock.

The fix: A short-term fix is to unplug any appliances that are on the same circuit as your air conditioner. This will alleviate the load of that particular circuit. For a long-term solution, have a professional electrician inspect your circuits and find a safe solution that will prevent another overloaded circuit.

Need a professional to check for problems?

If you aren’t sure whether your dimming lights are a problem, contact Energy Today’s electricians to inspect your home for any issues. We serve Tampa Bay, Central Florida, and SW Florida from our locations in Sarasota, Naples, Orlando, and Tampa.

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